DN hu v i) f nN a AHN)" », } \ th We roa ite Oh un Minin ity i ph Ale a ” Mh vey ‘ye NSA LNG ipa if RL BAR Digitized by the Internet Archive in 2009 with funding from Ontario Council of University Libraries http://www.archive.org/details/transactionsmic39ameruoft TRANSACTIONS | OF THE American Microscopical Society ORGANIZED 1878 INCORPORATED 1891 PUBLISHED QUARTERLY BY THE SOCIETY EDITED BY THE SECRETARY PAUL S. WELCH ANN ARBOR, MICHIGAN VOLUME XXXIX NuMBER Four ‘ Entered as Second-class Matter August 13, 1918, at the Post-office at Menasha, Wisconsin, under Act of March 3, 1879. Acceptance for mailing at the special rate of postage provided for in Section 1103, of the Act of October 3, 1917, authorized Oct. 21, 1918 The Dollegiate Press GrorGE BANTA PUBLISHING COMPANY Wags MENASHA, WISCONSIN q 1920 o OFFICERS Rrestdegtco Ts, Wy NGAELOWAY Secs Suc vis hotie Aetere beptve to elee orate New York City, N.Y. erst ll ecé-Prestaent:» CHANCEY) JUDAY.|- 1). 2: ciaceescor serine centers Madison, Wis. Second Vice-President: A. D. MACGILLIVRAY .............2.2020005- Urbana, Ill. Nepechigy:APAUE AO? WELCH? 55.05.20: = dct eae ee sere Ann Arbor, Mich. Tveasup er: NVILLIAM Fe EENDERSON? PE Hee erier seee noe eerie ene Pittsburgh, Pa. Gustadian:S MAGNUS), PELAUMS 5 './54 j4ccmep oocem aca Meee ee Philadelphia, Pa. ‘ ELECTIVE MEMBERS OF THE EXECUTIVE COMMITTEE FRANK GMITHE 1.) 2auy fie Sober seas teers te eee eat ee OTE eos ROE Ore aice te Urbana, Ill. POE ACKRRT cin meet mre eters tere se ee crc ee eer er eae Manhattan, Kansas. IBSEDSRVANSOMR yeep aie or 6c RE URN eee evs gO A a eat. a RE Washington, D.C. EX-OFFICIO MEMBERS OF THE EXECUTIVE COMMITTEE Past Presidents Still Retaining Membership in the Society Smon Henry Gace, B:S., of Ithaca, N.Y., at Ithaca, N.Y., 1895 and 1906 A. CiirForD Mercer, M.D., F.R.M.S., of Syracuse, N. Y., at Pittsburgh, Pa, 1896 C. H. EIGENMANN, Ph.D., of Bloomington, Ind., at Denver, Colo., 1901 E. A. BircE, L.L.D., of Madison, Wis., at Winona Lake, Ind., 1903 Henry B. Warp, A.M., Ph.D., of Urbana, IIl., at Sandusky, Ohio, 1905 HERBERT OsgBorNn, M.S., of Columbus, Ohio, at Minneapolis, Minn., 1910 F. D. Heatp, Ph.D., of Pullman, Wash., at Cleveland, Ohio, 1912 CHARLES BROOKOVER, Ph.D., of Louisville, Ky., at Philadelphia, Pa., 1914 Cartes A. Koror, Ph.D., of Berkeley, Calif., : at Columbus, Ohio, 1915 M. F. Guyer, Ph.D., of Madison, Wis., at Pittsburg, Pa., 1917 L. E. Grirrin, of Pittsburg, Pa., at Baltimore, Md., 1918 The Society does not hold itself responsible for the opinions expressed by members in its published Transactions unless endorsed by special vote. Vee ‘ i. TABLE OF CONTENTS For VoLuME XXXIX, Number 4, October 1920 Micro-Technique. Suggestions for Methods and Apparatus, with five figures, BANS ATCODD ceraetataic Seta Secale. Wiaiainiaysleisle ui Siovetatle austehe a sieiacers ateree ts wee 231 MBIS ERO Re VESTS yds eine eiscl ER es ee Re yc RCI, batons day RINNE ta ane EIS 243 Mndexitokv olume) XoXo. tartare alia, Phe yarn Hl chee uae ates Sun mich iiuee Rae a 254 i A aL, 2 Sa tA TRANSACTIONS OF THE American Microscopical Society ORGANIZED 1878 INCORPORATED 1891 PUBLISHED QUARTERLY BY THE SOCIETY EDITED BY THE SECRETARY PAUL S. WELCH ANN ARBOR, MICHIGAN VOLUME XXXIX NUMBER ONE Entered as Second-class Matter August 13, 1918, at the Post-office at Menasha. Wisconsin, under Act of March 3, 1879. Acceptance for mailing at the special rate of postage provided for in Section 1103, of the Act of October 3, 1917, authorized Oct. 21, 1918 The Collegiate Press GrorcGE BANTA PUBLISHING COMPANY MeEnNASHA, WISCONSIN 1920 OFFICERS President i. NV. AGALLOWANE Arise tise cetins tee eee teens New York City, N.Y. iRirsh Vice-President CHANCE Yo UDAVES rita seis ce eee ele eee Madison, Wis. Second’ Vice-President: A. D. MACGILLIVRAY ...:.-..-..-.+-+-5+-5:- Urbana, Ill. Secretary a PAU: Sep WiETCHig seer a emia (ei cise e sc star ieee Ann Arbor, Mich. E*COSUTET 3 NVILLTAREE. JELENDERSON: © eo essere nla sioe ae nese a 2) Rane siaeys Decatur, Il. Custodian: MAGNUS, PFUAUM See, 7 Aope asc as a eles caasla eyes exe Philadelphia, Pa. ELECTIVE MEMBERS OF THE EXECUTIVE COMMITTEE TECR ANIC SNGTTNET 3 hehe LF ALU btn eC Edo casos Se RE aC RE ST Urbana, Ill. Hy AY Nokon Peach in othe RE MOL peat lmia ib aM 8 tinloteio: elena aencloiG 0'o\e Manhattan, Kansas. BS HGIRANS OME AZINE dante Se ee aOR TOL ie Era te ae bee erwetc ty Svar teese: Washington, D.C. EX-OFFICIO MEMBERS OF THE EXECUTIVE COMMITTEE Past Presidents Still Retaining Membership in the Society Srmon Henry Gact, B.S., of Ithaca, N.Y., at Ithaca, N.Y., 1895 and 1906 A. CiirrorpD Mercer, M.D., F.R.M.S., of Syracuse, N. Y., at Pittsburgh, Pa, 1896 A. M. Bierte, M.D., of Columbus, Ohio, at New York City, 1900 C. H. E1rcenmann, Ph.D., of Bloomington, Ind., at Denver, Colo., 1901 E. A. Birce, L.L.D., of Madison, Wis., at Winona Lake, Ind., 1903 Henry B. Warp, A.M., Ph.D., of Urbana, IIl., at Sandusky, Ohio, 1905 HERBERT Osporn, M.S., of Columbus, Ohio, at Minneapolis, Minn., 1910 A. E. Hertzirr, M.D., of Kansas City, Mo., at Washington, D. C., 1911 F. D. Heap, Ph.D., of Pullman, Wash., at Cleveland, Ohio, 1912 Cartes Brooxover, Ph.D., of Louisville, Ky., at Philadelphia, Pa., 1914 Cuartis A. Koror, Ph.D., of Berkeley, Calif., at Columbus, Ohio, 1915 M. F. Guyer, Ph.D., of Madison, Wis., at Pittsburg, Pa., 1917 L. E. Grirrin, of Pittsburg, Pa., at Baltimore, Md., 1918 The Society does not hold itself responsible for the opinions expressed by members in its published T'ransaciions unless endorsed by special vote. TABLE OF CONTENTS FOR VOLUME XXXIX, NUMBER 1, January 1920 Glaridacris catostomi gen. nov., sp. nov.: A Cestodarian Parasite, with Plates I SUILCM OE Rat Diya RSC GODT aq acne ci Aaa MOON ai sal a ne RIG ahem Le SIRI SEARS The Genera of the Enchytraeidae (Oligochaeta), by Paul S. Welch............. An Ecological Study of the Algae of Some Sandhill Lakes, by Emma N. Andersen aoe ani Wal en ete in Amey TONED AU Ui umn mrbene ya AN repie sm Mine EA URE Ae Notes and Reviews: Leeches considered as Oligochaeta Modified for a Predatory nile Hrevile wean bye PaySMIE Ls rae ecie ie Mente he) GUIS Leelee cra a ene RU ner NS) Sea Wea uibesior the St NMouis vi cetiney yng kee L312 ly hale ture WN gal be Laat RPE pOn On the Neu storbamiay aia unt ON ean tae tra Ahh alt SRT hh cag en Mies MPRA ReHOn orien PECASUPCN cc. 4 meat e is Tirta sha tey by eget Nile) ahs A eMail LAGAN aia as ie Pe eae pa eey 4) TRANSACTIONS OF American Microscopical Society (Published in Quarterly Instalments) Vol. XXXTX JANUARY, 1920 No. 1 GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV.: A CESTODARIAN PARASITE By A. R. CooPER INTRODUCTION In a preliminary paper Ward (1911) stated that he had found in fish from the Illinois River a cestodarian tapeworm which showed certain features common to the well known European genera, Caryo- phyllaeus and Archigetes. ‘It resembles the former in the absence of a caudal appendage and in the location chosen by the adult para- site, viz., the intestine of a fish, whereas, so far as known in Europe, Archigetes always possesses a tail and has been found only in the body cavity of tubificid worms. In general appearance and structure the American form resembles the European Archigetes very strongly. It has a scolex of fixed form with prominent suckers or phyllidea and also the musculature of Archigetes. The general arrangement of the reproductive organs, especially the two rows of testes in the central field, and the genital pores, correspond also closely to conditions in Archigetes.”’ Much later the same writer (Ward and Whipple, 1918) merely stated in his key to the Cestodaria that, as regards Archigetes, “a form which undoubtedly belongs here has been described to me as found in native earthworms.” Neither under Archigetes nor under Caryophyllaeus does he make any further mention of the above form, and concerning Amphilina says only: ‘Not yet reported from North America but present.’”? Nor have I been able to locate any other reference to members of the Cestodaria, sensu latu, having been found on this continent up to date. Before proceeding with the detailed account it mHeuld be men- tioned as a matter of introduction that, apart from being evidently 6 A. R. COOPER the first member of the group to be described from America, the spe- cies to be dealt with here is of special interest in that it seems to stand intermediate in the family, Caryophyllaeidae Liihe 1910, between Archigetes and Caryophyllaeus. Excepting for the scolex, however, which is quite similar at least in outward appearance to that of Archigetes brachyurus Mrazek, it closely resembles the species of Caryophyllaeus, of which three, namely, C. laticeps (Pallas), C. tuba (Wagener) and C. fennicus Schneider, have been found in Europe, and one, C. syrdarjensis Skrjabin, in Asia (Turkestan). MATERIAL The material for the present study was obtained at the Douglas Lake Biological Station of the University of Michigan during the summer of 1917 while the writer was paying particular attention to the bothriocephalid cestodes of fishes. In all thirty-six specimens of Catostomus commersonii (Lacépéde), the host species, were examined. These fell into two lots as regards size: ten younger ones ranging in length from 90 to 115mm. and twenty-six adults from 250 to 325mm. The latter were caught in the trammel and fyke nets used in the lake proper, while the former were seined out of Maple River which drains the lake. No parasites belonging to the species described here were met with in the younger hosts, but from two to at least sixty-three were found in the stomachs and intestines of eleven of the adults. The table shown on page 7 gives their number, distribution and kind in nine of the hosts, the exact numbers not having been recorded for the other two fish. From this it is seen that the degree of infestation of the host is comparatively small. Whereas the number of adults met with was quite limited, larvae were very plentiful when present at all. In situ all of the adults and most of the larvae were found free in the stomach or intestine, but many larvae—forty-one in the case of the third fish in the table—were attached to the bottoms of deep pits in the mucosa of the pyloric region of the stomach. These pits were not mere depressions of the wall of the stomach but actual cavities, as shown in figure 7, bordered by a pronounced annular thickening of the mucous membrane and as much as 2mm. in dia- meter. Larvae ranging in size from almost the smallest met with to those near the adult stage in development were tightly crowded into these pits and at the same time strongly contracted longitudinally. GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. § 7 STOMACH INTESTINE Length of host Number Kind Number Kind Arey ATCA ee Re Yat. HOO LE ae 9 A UltS Wire ha ee ieee neta abled cise PSO eaboals Rory eerree rieneiiet iret ie 4 AGAUILES TPMT Carat Rie ce aaron [tal tes ed shave ellen 14 GAVE NN cara) Cslape Vey reg ares ees een ae op stare ae atte PT S\ Tato 2 RS oleae ee eo 63 Orb aveg: Kew) PADRE RIN Phets Aneta Ea AtAh omib ete iat BLS} Teak sR Selle yest a ey Adee | eheoreT eG A ier Aaa] [CO TAA ina AL 2 Larvae IX) TIN GO ho Ren aoe MAA oe 9 Larvae 52 Larvae PADIS) Saale hw ee RIN US OD a IRS IDE EA AN IS Le GET ek Re UL 2 Adult 1 Larva DOSWIMNIN< iio ek his ke 7 Larvae 21 Larvae ZEON SUS sec ke tote let ane [ata ee Ole meee oe eee os 20+ Larvae DADS Sr aaa als, on pa dey TRIS eal RE Se eR esl (Ae teat arene eo kaernee 12+ Larvae EXTERNAL FEATURES On account of its possessing a well developed musculature for its size this species exhibits considerable differences in degree of contrac- tion and elongation on fixation. If no care is taken in applying the fixing reagent nor in slightly manipulating the specimen, it usually contracts to such an extent that it becomes almost useless, at least for the making of toto preparations. However, the adults, which are here considered to be those whose uteri may be seen in toto preparations to contain a few or many eggs, may be said to range in length from about 5 to 25mm. and from 0.4 to 1.0mm. in maximum breadth. In immature individuals the scolex, when not strongly contracted, has somewhat the form of a truncated rectangular pyramid with the longer diameter in the transverse direction. As shown in figures 1 and 2, the edges of the base and the apex protrude markedly, in the latter case forming a terminal disc comparable to that of many of the bothriocephalid cestodes. The dorsal and ventral faces of the organ are each divided by two ridges converging towards the apex into three sucking grooves or loculi, of which the middle is best devel- oped and most efficacious during life. It is also the last to become smoothed out with strong contraction of the whole scolex. The lateral loculi are, furthermore, not in the same plane with the medial one but inclined towards the corresponding ones of the opposite surface so that the edges of the scolex, especially just behind the 8 A. R. COOPER terminal disc, are often not much thicker than the ridges between the loculi. As regards these features the organ consequently resem- bles that of Archigetes brachyurus Mrazek 1908, which is here repro- duced (Fig. 5) for the sake of comparison. In adults, on the other hand, the edges of the terminal disc are usually found in preserved material to be contracted to the point of obliteration, so that the whole organ is shaped more like a wedge or chisel with oftentimes rather thick margins (Figs. 3, 4 and 9). As a matter of fact the scolex of this form assumes a greater variety of shapes than that of any other tapeworm I have yet examined, in which respect it is comparable to the leaf-like anterior end of Caryophyllaeus. The dimensions of the organ are as follows: Length, 0.30 to 0.45mm.; width (posteriorly), 0.45 to 1.10mm.; depth (posteriorly), 0.50 to 0.75mm. Behind the scolex the strobila narrows down for a short distance and then much more gradually enlarges again to the region of maxi- mum diameter, which is usually behind the genital openings. Yet in many specimens, especially the more relaxed ones, the whole strobila is all but uniform in width thruout its length. The region between the scolex and formost vitelline follicles, which includes the narrowest portion of the strobila and is consequently called the neck, varies from 1.5 to 2.5mm. in length. Finally the posterior end, as shown in figure 6, is somewhat triangular in outline with a slightly indented tip where the excretory vessels open to the exterior, but bears nothing in the nature of an appendix such as it present in Archigetes. CUTICULA, SUBCUTICULA AND PARENCHYMA The cuticula, which varies in thickness from 7 to 11, is bounded on the inside by a comparatively heavy basement membrane, about one-sixth of the thickness of the whole layer, and on the outside by a smooth membrane about one-half as thick as the basement mem- brane. The remainder of the tissue has the appearance of a reticulum enclosing numerous distinct granules. This reticulum is in reality a meshwork of fine canaliculi which freely pierce both limiting membranes, thus giving them the appearance in tangential sections of fine sieves. Nowhere is the cuticula modified to form spinelets nor distinct cirri, altho over the scolex it is considerably folded and GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 9 irregular, the outer membrane being all but absent, especially within the suckers. For Caryophyllaeus laticeps Will (1893) described a cuticula 5 to 6m in thickness and composed of only two layers, an outer showing radial striping, as if formed by fine bristle-like hairs, and an inner, more deeply staining stratum, comparable to the basement membrane of this form. He saw no distinct pores in the cuticula, and thought that perhaps the striations might represent prolongations of the subcuticula. The subcuticula is made up of large flask-shaped cells, closely crowded together and provided with comparatively large nuclei. Whereas the individual cells are not distinctly separated from one another, the whole layer, from 90 to 100, in thickness, is clearly marked off from the underlying parenchyma owing to the very granular nature of its components. The nuclei, which are spherical to oval in shape and provided with distinct spherical nucleoli, vary from 16 to 18 in greatest diameter. They are located at different levels, so that the whole layer has a pseudostratified appearance. The enlarged central ends of the cells are usually rounded off towards the parenchyma, which feature is clearly indicated by their character- istically large granules. On the whole the subcuticula is not very different from that of C. laticeps as described by Will. The parenchymatous cells form an open reticulum showing only a very few nuclei. They are in strong contrast with the subcuticular cells on account of their clear, non-granular cytoplasm. .Posteriorly the whole tissue is much limited in amount by the large reproductive organs which are imbedded in it. No such “fibrous strands” of modified parenchymatous cells, as described by Will for C. laticeps and by Skrjabin for C. syrdarjensis, were seen in thisform. In the base of the scolex and in the neck region, however, the medulla is occupied by a more or less X-shaped mass of cells (Fig. 10) containing large nuclei with numerous large granules which have a great affinity for the counterstain. They are probably glandular in their nature since they send long processes, especially in the diagonal direction, to the cuticula covering the scolex, between the cells of the subcuticular layer. Furthermore, no evidence of the presence of calcareous bodies in the parenchyma was met with in an examination of both fresh and preserved material. 10 A. R. COOPER MUSCULATURE The musculature is comparable to that of the cestodes proper in that it is composed of two sets of fibres, the parenchymatous and the cuticular. The former consists of sagittal (dorsoventral), frontal (transverse) and two sets of longitudinal fibres, of which the latter are much the strongest. Whereas both sagittal and frontal fibres are few in number, they are not equally so, for the sagittal are somewhat larger and more numerous. Both kinds tend to course slightly obliquely where they are greatly interfered with by the reproductive organs. The main or inner longitudinal fibres are, on the other hand, comparatively large and arranged in thick bundles (Figs. 11, 12 and 13). They are situated among the central ends of the subcuticu- lar or just within them, the cortical parenchyma being thus consider- ably restricted in amount. Posteriorly the fasciculi are very unequal in size and quite numerous. As they are followed forward, however, their numbers diminish while their size increases, until at the base of the scolex there are only eight large bundles arranged as in figure 10. This is brought about by the fusion of the smaller bundles and the passage of the fibres from one fasciculus to another. In longitudinal sections the bundles are irregularly striated owing to there being a considerable amount of myoplasm in the middle of each fibre around the remains of the original myoblastic nucleus. Nevertheless, no distinct nuclei such as described and figured by Will for C. laticeps were seen. In the posterior end of the worm many of these longi- tudinal muscles terminate in the walls of the excretory invagination or run alongside of it to the extremity of the strobila. The outer longitudinal group (Fig. 10) consists of a large number of bundles, smaller but more uniform in size than those of the inner group, situated among the peripheral ends of the subcuticular cells just outside of their nuclei or from 15 to 30u from the cuticula. Posterior- ly only a few of them pass beyond the anterior end of the excretory invagination, but anteriorly they are very pronounced and continue into the scolex. Similar fibres in C. laticeps were considered by Will to belong to the cuticular instead of to the parenchymatous series. The cuticular muscles consists of an outer stratum of circular fibres lying close to the inside of the cuticula and an inner of longi- tudinal fibres situated close within that. The longitudinal fibres, which in some places intermingle slightly with some of the outermost GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 11 members of the outer longitudinal parenchymatous group, are arranged in small bundles, each containing at most only about ten or a dozen fibres. In the posterior end of the worm they proceed farther back than the latter, after being closely associated with them opposite the excretory invagination. The same may be said of the circular cuticular muscles, excepting that they are not distinctly arranged in bundles. In the scolex the cuticular muscles are much less pronounced over the sucking-grooves than on the lateral faces. As shown in figure 9, the eight large bundles of inner longitudinal muscles, mentioned above, are arranged so that four form two sagittal pairs situated towards the lateral faces, while the other four, somewhat larger ones form two other sagittal pairs, each about half way between the nerve trunk and the median line. These are distributed in a radiating manner to the corresponding portions of the tip of the scolex, the median pairs going to the ridges between the loculi and the neighbor- ing parts of the latter. On the whole their attachment is similar to that of the main longitudinal group in C. tuba and C. laticeps, as described respectively by Monticelli (1892) and Will. The outer longitudinal muscles are more numerous on the lateral surfaces of the scolex than opposite the suckers, to the cuticula of which they are easily traced. The loculi are also provided with a few scattered radiating fibres, lying in both the longitudinal and the transverse directions, and comparable to those used in the Pseudophyllidea for the enlargement of the bothria. They are, however, of much less functional importance in that connection than the sagittal and transverse fibres, which are somewhat larger and more numerous than in the middle of the worm. In fine, the musculature of the scolex is poorly developed as compared with that of Bothriocephalus, s. str., for example, which fact is shown in the great diversity of shapes of the organ in preserved material. In fact it might be considered to represent an intermediate stage between that of the anterior end of Caryophyllaeus and that of the typical bothriocephalid scolex. But the comparative inefficiency of the individual sucking- grooves is compensated for by their number and by their manner of attachment to the host’s alimentary tract, namely at the bottom of the spacious pits described above. 12 A. R. COOPER NERVOUS SYSTEM The nervous system consists of a pair of ill-defined longitudinal trunks and two equally indistinct and diffuse terminal ganglia situated in the scolex, into which they pass. The main strands can be fol- lowed more or less easily in material not especially treated to demon- strate them only in the neck region. There, as shown in figure 10, they are situated symmetrically in the median frontal plane within the trapezium formed by the two pairs of main longitudinal muscle bundles, much closer, however, to the lateral pair than to the more median pair. They supply these muscles with large branches. Whereas in the neck they are fairly uniform in diameter—which varies from 18 to 30u—behind the most anterior vitelline follicles they become quite irregular in transection, all but disappearing in places. In the middle of the worm and posteriorly they seem to break up into a diffuse plexus lying just within the subcuticular cells, that is, among the numerous bundles of the inner longitudinal muscles. No collateral strands such as the eight described by Will for C. laticeps were seen in this form. In the base of the scolex these chief nerve strands expand con- siderably in the dorsoventral direction and become united by a few transverse fibrils. Farther towards the tip, however, each of these enlargements divides into two parts sagittally, and each of the latter unites with its fellow of the opposite side by a loose strand of trans- verse fibrils, so that two anteriorly directed loops are thus formed. On the whole the nervous system is comparatively poorly developed, since not only the chief strands but also their connections in the scolex are composed of very fine, indistinct and loosely arranged fibrils. EXCRETORY SYSTEM Thruout most of the length of the worm the excretory system consists of a single layer of comparatively large and much coiled longitudinal vessels situated just outside of the inner longitudinal muscles among the central ends of the subcuticular cells. Whereas the number of these vessels cannot be stated definitely, owing to many transverse connecting channels, there is a tendency, especially in the anterior regions, for eight of them to take the courses indicated in figure 11. Three are located on each surface and one in the median frontal plane at each side. In the anterior part of the neck region GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 13 the number increases, and the courses of these vessels become irregular, that is, the plexus becomes more diffuse. There they invade all parts of the subcuticula and the periphery of the cortical paren- chyma (Fig. 10). From 1 to 1.5mm. behind the tip of the scolex two branches leave the plexus above and below the nerve cord on each side (Fig. 10) and unite on the medial side of the latter to form one vessel. In these positions the two vessels thus formed pursue spiral courses forward and apparently unite close behind the nerve com- misures mentioned above.. For C. laticeps Fraipont (1880) and Will described an excretory system consisting in brief of four ‘ascending canals” and ten ‘descending canals,’’ connected in the mobile anterior end of the worm with each other and posteriorly with the so-called excretory vesicle. Thus it is seen that as regards the main channels of the excretory system at least this species is somewhat less com- plicated in structure than the European species in question. In the posterior end of the former the plexus just described converges towards the centre of the medulla, as the vessels diminish in size, and unites by several openings with the terminal receptacle. The latter, as pointed out for C. laticeps by Steudener (1877), is merely an invagination of the hinder end of the worm, about 0.25mm. in length by about 0.05 in diameter. Its wall is composed of only a lining of cuticula continuous with that covering the posterior end of the worm and also traceable for some distance into the larger branches leading from the plexus into the invagination. In the sections made it was also seen to be quite vacuolated and granular and poorly pro- vided with cuticular muscles, thus indicating that the whole structure is not a true pulsating vesicle. Nowhere in any of the sections studied was I able to find the typical terminal organs of the excretory system, namely, the flame- cells, which according to Fraipont are present in C. laticeps with the same structure as those in trematodes. But in their place there appeared much less specialized cells which are, nevertheless, com- parable in some respects to the ciliated funnels of other cestodes. As shown in figure 8, each consists of a large cell provided with a large nucleus with a distinct spherical nucleolus but much vacuolated cytoplasm. The cytoplasm is aggregated close around the nucleus, and from this mass numerous strands pass to the wall of the cell. The latter is directly continuous with one or more canaliculi which lead off from the structure and connect up with the larger vessels 14 A. R. COOPER to form the plexus. The whole has the appearance of an enlarge- ment of the terminal vessel, enclosing an amoeboid cell which is sus- pended in the centre of the vesicle by its pseudopodia. Thus the vacuolated space which surrounds the cytoplasmic mass and is continuous with the cavity of the canaliculi is comparable in part at least to the funnel which accommodates the “flame” in the typical flame-cell. . These terminal organs are situated close around the canals in the periphery of the cortex or even farther out among the inner ends of the subcuticular cells. Furthermore, they are much more numerous in the neck region than elsewhere. The only reference I have been able to find to structures at all comparable to these peculiar cells is that by Wright and Macallum (1887) on Sphyranura oslert. For this form, a monogenetic trematode, they described as the terminal renal organs peculiar elongated, club-shaped cells which are situated in close proximity to the vitelline follicles and the principal groups of muscles. The cytoplasm of the cell is divided into a number of coarse, granular trabeculae radiating from the nucleus to the wall, thus leaving a system of communicating spaces, “empty in the fixed, but often unobserved in the fresh, condition. . . . Each cell has a process at one pole, with an axial wavy channel connected with one of the neighbouring excretory capillaries . . . , the wall of which passes insensibly into the membrane of the cell.” Perhaps also certain large amoeboid cells with nuclei filling up almost the whole of the cell and large nucleoli surrounded by clear areas, found by Will in specimens of C. Jaticeps fixed in Flemming’s solution and crude acetic acid and described under the nervous system, may rightly belong to this category of peculiar excretory cells. REPRODUCTIVE ORGANS On the whole the reproductive organs of this species (Fig. 6) closely resemble those of the species of Caryophyllaeus. In the longi- tudinal direction they extend from 1.5 to 2.5mm. behind the scolex, where the foremost vitelline follicles are situated, to the posterior end of the worm. The openings and the central connections of the ducts are located, however, near the posterior end, the former, in fact, only from 1.5 to 2.8mm. from the tip, depending on the degree of contraction of the specimen. Excepting Skrjabin, the European writers emphasize in their descriptions of the species of Caryophyl- laeus the fraction of the whole length of the worm occupied by the GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 15 organs behind the opening of the cirrus. For C. tuba the latter opens at the beginning of the last quarter of the body, for C. laticeps at the beginning of the last fifth, and for C. fennicus in the last fifth. Skrja- bin says only that in C. syrdarjensis the ovary is situated in the posterior third of the body. Owing to very considerable differences in degree of contraction and elongation it seems to me that, at least so far as the present species is concerned, these proportions are not of specific value. On account of the greater development of the muscu- lature anteriorly that portion of the body ahead of the genital openings is much more variable in length than that behind the apertures—hence the above measurements for the latter only. The genital openings are situated in the midline on the ventral surface from 0.5 to 1.0mm. apart. The cirrus-opening is somewhat transversely elongated and about 0.15mm. in diameter. The opening of the female atrium has the form of a shallow, transverse, crescentic groove, about 0.35mm. in width, with its concave side directed anteriorly. Both apertures are so close together in most of the specimens at hand that they are located at the bottom of a common depression; or, the slight depression accommodating the male opening. runs insensibly into the crescentic female atrium. Male genitalia.—The testes (Fig. 11) are not entirely surrounded by the vitelline follicles as in C. laticeps and C. syrdarjensis. Anter- iorly they begin at the same level as do the latter, and posteriorly they extend to the cirrus-sac or in some cases slightly beyond its anterior border. They are irregularly ellipsoidal in shape, and have lengths, widths and depths of from 0.135 to 0.227, 0.100 to 0.145 and 0.127 to 0.181mm., respectively. Their number as determined by direct count and by calculation from the average number in longitudinal and transverse sections varies from 150 to 160. They are especially noteworthy on account of their showing the various Stages of spermatogenesis with almost diagrammatic clearness, a fact which was also noted by Monticelli in the case of C. tuba and by Skrjabin in his description of C. syrdarjensis. Nevertheless in none of the series of sections cut were any spermatozoa seen in any part of the vas deferens, altho the uteri were in the same preparations well filled with eggs. This would seem to indicate that contrary to the usual procedure among cestodes the female genital organs develop before the male organs and that self-fertilization does not take place. 16 A. R. COOPER The vas deferens forms a loose and somewhat triangular mass of coils about 0.32, 0.28 and 0.36mm. in length, width and depth, respectively and situated immediately ahead of the cirrus-sac. Just before entering the latter it expands into a muscular vesicula seminalis having a diameter of from 65 to 90 and a length of about 0.30mm.; but at its beginning it has no seminal reservoir like that attributed to C. laticeps by Will. The wall of the duct consists of a lacerated or pseudociliated, syncitial epithelium, provided with widely separated nuclei—excepting in the seminal vesicle where they are fairly numer- ous—and resting on a basement membrane. The musculature of the vesicle consists of numerous circular fibres with a few oblique fibres distributed among them. Entering the cirrus-sac anterodorsally with a diameter of 30u, the vas deferens expands in the dorsal third of the latter to form a sort of secondary, but doubtless only temporary, seminal vesicle averaging 60 in diameter. After taking several turns it gradually diminishes to about 35m in the mid-region of the sac and passes insensibly into the cirrus proper. The structure of the wall of the duct within the sac up to this point is the same as that of the seminal vesicle just outside of the sac. The cirrus, which occupies the lower half of the cirrus-pouch, is a comparatively large closely coiled tube with a diameter of 60 to 65yu. Its wall, which is much cleft and folded on account of the length of the organ, is similar in structure to that of the vas deferens, excepting that the number of circular muscu- lar fibres is much greater and that the imperfect epithelium of the latter is replaced (in the transitional region) by smooth cuticula, continuous with that of the ventral surface of the worm as in the cestodes proper. Altho in the material at hand there were no cases of extruded cirrus, its structure and disposition within the sac is such as to lead one to believe that when it is evaginated it is a compara- tively long and stout organ. The cirrus-sac (Fig. 12) is ellipsoidal in shape and occupies the whole of the medulla of the region dorsoventrally and almost all of it laterally. Its length, width and depth are, respectively, 0.40 to 0.50, 0.50 and 0.50 to 0.60mm. Its wall is composed of mus- cular fibres running in all directions and not sharply separated from the retractor muscles within the organ. A few dorsoventral fibres pass from the top of the sac to the dorsal body-wall and a few from GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 17 the equatorial region to the ventral body-wall. The contents of the Sac are composed of numerous and very compactly arranged retrac- tor muscles, their myoblastic nuclei and a small amount of parenchy- matous tissues. Female genitalia.—Into the dorsal portion of the female genital atrium, which is about 0.25mm. in depth and lined with a much lacerated continuation of the cuticula from the ventral surface of the worm, the vagina empties slightly to one side of the median line, the other side accomodating the opening of the uterus. From the atrium it passes backward in the median line (Fig. 6) beneath, or at some levels almost surrounded by, the coils of the uterus. Its diameter near the opening varies from 50 to S5yu, but half way along its course this is reduced to 30y. Thruout its length its wall is composed of a lining of cuticula 5u in thickness and surrounded by numerous circular muscles only, the myoblastic nuclei of which form a rather distinct stratum about 10 distant from the fibres. At the level of the posterior end of the ovary it opens into the oviduct with a diameter of 84 and a much reduced cuticular lining and layer of circular muscles. Unlike that of C. laticeps, as described by Will, it is nowhere enlarged to form a receptaculum seminis. The ovary is situated usually half way between the genital openings and the posterior end of the animal (Fig. 6). It is from 0.8 to 0.9mm. in length and consists of a stout almost spherical isthmus, about 0.4mm. in diameter, from which numerous, irregular and thick lobules pass upward and slightly forward to enclose a capa- cious generative space. In the latter respect this form resembles not only the species of Caryophyllaeus but also Cyathocephalus and Bothrimonus as described elsewhere by the writer (Cooper, 1919). As shown in figure 13, the lobules lie in the periphery of the medulla, close to the main longitudinal muscles. Ova near the beginning of the oviduct average 15y in diameter in sections, and are composed almost entirely of the nucleus, there being very little cytoplasm. A distinct and almost spherical nucleolus taking the counterstain very readily is to be seen in each nucleus. The oviduct begins at the posterior end of the isthmus and somewhat ventrolaterally in an oocapt, 254 in diameter by 20u in length and provided with only a few circular muscles. About 125 from the oocapt it is joined by the vagina. This first portion 18 . A. R. COOPER of the oviduct is 25 to 30u in diameter, and takes a dorsal course. Its walls are composed of a thin but uniform layer of circular muscu- lar fibres on the outside, and on the inside of a comparatively thick layer of epithelium, the cells of which are not clearly separated from each other but contain relatively large and deeply staining nuclei. After passing backward and upward about 404 beyond the point of union with the vagina the oviduct receives the common vitelline duct. As in the species of Caryophyllaeus the vitelline follicles are located in the medulla in two distinct and separate regions: a large one extending from 1.5 to 2.5mm. behind the tip of the scolex to the cirrus sac, and a much smaller one in the more or less conical posterior end of the worm behind the coils of the uterus (Fig. 6). In the former situation they form an irregular layer in the periphery of the medulla (Fig. 11), for not only do some dip down among the testes, as mentioned above, but others extend outward to the main longitudinal muscles; in the latter, however, they occupy almost the whole of the medulla, as in C. laticeps. In the immature worm there is, furthermore, some tendency for them to be arranged in two lateral fields anteriorly, leaving a free strip in the median line dorsally and ventrally. In the anterior region in particular they are very numerous, irregularly ellipsoidal in shape, and vary greatly in size. From 8 to 14 appear in transections, while their maximum diameter is 0.20mm. Posteriorly they are slightly larger. The process of the formation of the peculiarly clear yolk-cells which are to be seen in the vitelline ducts (Fig. 14c) can be followed with a considerable degree of satisfaction in the follicles. The cyto- plasm of the small peripheral primordial cells from which they develop is very compact, and consequently stains deeply as does the nucleus (Fig. 14a). Numerous vacuoles appear in it and quickly enlarge, so that in the intermediate stages the nucleus appears to be suspended in the centre of the cells by protoplasmic strands radiating from it to the cell-membrane, as shown in figure 14b. These strands become modified into numerous, spherical deutoplasmic granules, migrate outward and eventually come to lie just inside the cell- membrane (Fig. 14c). In the proximal part of the uterus, where from four to six vitelline cells are seen to be associated with each fertilized ovum in the formation of the egg, the nucleus enlarges still GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 19 more and becomes more transparent, while the cell-wall gradually breaks down, thus liberating the vitelline granules. The enlarged nuclei remain intact, however, during the passage of the egg thru almost the whole length of the uterus. The common vitelline duct varies in diameter from 30 to 75y, and is lined by an epithelium similar to that of the oviduct. It is largest immediately dorsal to the posterior end of the ovarian isthmus where it forms a vitelline reservoir, as in C. /aticeps, as much as 220yu in width by 45y in depth when filled with yolk. A little farther forward it receives two main tributaries, varying considerably in calibre according to the amount of vitelline material they contain. Whereas these two ducts collect chiefly from the follicles ahead of the uterus, at least one small tributary on each side drains the follicles situated in the posterior end of the worm, and unites with the main ducts near their point of union with each other. Shortly after being joined by the common vitelline duct and as it courses a little farther back on one side or the other, the oviduct becomes surrounded by a poorly developed shell-gland. The ootype is consequently inconspicuous. Beyond the ootype the epithelium is syncitial in its nature since no distict cell-boundaries appear. More than its inner half is deeply cleft to form pseudocilia, yet its nuclei _ are comparatively large. As the oviduct—now, more properly called the beginning of the uterus—continues backward in a dorsal position in the medulla, it gradually enlarges, according as it becomes filled with eggs, its wall becomes thinner and thinner, and the nuclei diminish in number, flatten out and eventually disappear. The latter takes place particularly after the organ turns in its course— just ahead of the posterior group of vitelline follicles—and starts forward towards the female genital atrium. From a point just behind the level of the posterior border of the Ovarian isthmus to its opening the uterus is surrounded by a volumi- nous mass of club-shaped, unicellular glands (Fig. 13), similar to those described for the species of Caryophyllaeus and closely resem- bling those described by the writer (1919) for Cyathocephalus ameri- canus and Bothrimonus intermedius. As to the function of these cells no definite statements can be made as yet. Monticelli likened the similar cells in C. tuba to those to be seen along the uteri of many trematodes as well as of Gyrocotyle urna (Wagener), and called them 20 A. R. COOPER glutin-producing glands. Will described them in C. laticeps, and said that they were “‘fully identical” with those in Diphyllobothrium latum. He also incidentally mentioned that Saint-Remy (1890) looked upon them as a shell-gland. Schneider (1902) called them glandular cells in C. fennicus, while Skrjabin considered them to be shell-glands in C. syrdarjensis. In view of the fact that, as in the species of the subfamily Cyathocephalinae just mentioned, the shell- gland surrounding the ootype is poorly developed—altho it was clearly seen in this species to initiate the formation of the egg-shell— they may act as an accessory shell-gland. Even tho this whole region of the uterus is lined with a deeply cleft cuticula, numerous droplets of material were seen in the sections studied adhering to or lying among the pseudocilia as if they were secreted from the cells in question; and it is only in this portion of the uterus, not in the thin- walled proximal region, that the shells of the eggs are thickest. At any rate, since the uterus is provided with only a very few scattered circular muscles, excepting just before its opening, they cannot be myoblastic in their nature. Distally they diminish considerably in number, yet they are directly continuous with the myoblastic nuclei of the more numerous muscular fibres surrounding the terminal portion of the duct and the female atrium, which in turn are continuous with the subcuticular cells around the atrial opening. As stated above, the uterus opens into the female genital atrium ahead of and slightly to one side of the vagina. The atrium itself is from 0.20 to 0.30mm. in length by about 0.10mm. in diameter and lined with a very irregular and deeply cleft cuticula. The mature fresh eggs, when examined in normal saline solution, were found to be ovoid in shape and from 54 to 66y in length by 38 to 484in width. The shell is from 2 to 3yu in thickness, and is provided at its larger end with a small button-like boss and at its smaller end with an operculum from 12 to 16y in diameter. LIFE HISTORY As regards the development and life-history of this species only a few statements can be made at present. Larvae as small as that shown in figure 15 were found in the stomach of the host, but, altho a thoro dissection of the food-contents, which consisted of larvae of Chironomus and Simulium, Ostracoda, Cladocera, “‘caddice-worms,”’ GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 21 dragon-fly nymphs and Mollusca, was made, their mode of entrance was not discovered. Possibly further search will show that some member of these groups of animals, if not a tubificid worm as in Europe, is the intermediate host. Finally, from the standpoint of the systematic position of the species it should be emphasized that the smallest larvae found had nothing whatsoever in the nature of appendages. SYSTEMATIC POSITION From the above description it is clear that this species, altho a member of the family Caryophyllaeidae Liihe 1910, does not belong either to Archigetes or to Caryophyllaeus. As pointed out above, the scolex resembles that of at least one species of Archigetes, namely, A. brachyurus Mrazek, but is quite different from the simple, leaf-like anterior ends of the species of Caryophyllaeus. The reproductive organs, it is true, are much more comparable to those of the latter, but certain features of the muscular, excretory and nervous systems do not permit of its being placed in either genus. Consequently a new genus is erected to accommodate this form, and is given the following characters: Glaridacris gen. nov. With the characters of the family. Medium sized caryophyllaeids with the anterior end modified to form a scolex, provided on each surface with three suckers, of which the median one is the deepest and most efficacious. Main longitudinal paren- chymatous muscles in eight large fasciculi in the anterior part of the neck and the base of the scolex. Only two main nerve strands in the medulla, connected in the scolex by two more or less diffuse commissural loops. Excretory vessels form a single cortical plexus with eight principal longitudinal channels; no true flame-cells present, terminal renal organs, peculiar, highly vacuolated, simple cells. Expansion of the vas deferens before entering the cirrus-sac to form a vesicula seminalis. 6dAapis, chisel; axpvs, summit. Type, and as yet only, species: G. catostomi sp. nov. The principal specific characters may be set down as follows: Glaridacris catostomi sp. nov. With the characters of the genus. Small cestodarians, up to 25mm. in length by 1.0mm. in breadth. Scolex, short and broad, chisel-shaped in older specimens, hexa- gonally pyramidal with prominent terminal disc in younger, base large in both; length, 0.30 to 0.45mm., width (posteriorly), 0.45 to 1.10mm., depth (posteriorly), 0.50 to BZ A. R. COOPER 0.75mm. Neck only slightly narrower than body, 1.5 to 2.5mm. in length; whole worm, apart from scolex, cylindrical, with somewhat conical posterior end. Cuticula, 7 to 11 in thickness; subcuticula, 90 to 100u. No “fibrous strands’ nor calcareous bodies in parenchyma. Female genital atrium, 0.5 to 1.0mm. behind opening of cirrus, 0.20 to 0.30mm. in depth by 0.10mm. in diameter, opening crescentic, in same depression with male opening. Testes not completely surrounded by vitelline follicles; extend to cirrus-sac pos teriorly; irregularly ellipsoidal in shape, from 0.10 to 0.18mm. in different diameters; 150 to 160 in number. Vas deferens, a loose somewhat triangular mass ahead of cirrus- sac, 0.28 to 0.36mm. in diameter. Vesicula seminalis, 0.30 by 0.06 to 0.09mm. Cirrus-sac large, almost spherical, occupying almost whole of medulla of region, 0.40 to 0.60mm. in diameter. Cirrus, 60 to 65 in diameter. Vagina median, ventral, 30 to 55y in diameter. Ovary irregularly lobular, 0.8 to 0.9mm. in length, with nearly spherical isthmus, 0.4mm. in diameter. Oocapt, 20 by 25. Vitelline follicles not completely surrounding the testes, 8 to 14 in transec- tions, 0.20mm. in maximum diameter. Vitelline reservoir, the expanded common vitelline duct, 220 by 454. Ootype inconspicuous. Uterus in two portions, a proximal, thin-walled, and a distal, extending from the posterior vitelline follicles to the opening and surrounded by a large number of unicellular glands; empties into female atrium slightly ahead of and to one side of vagina. Eggs, ovoid, with small boss at larger end, 54 to 66y in length by 38 to 48y in width. Habitat: In stomach and intestine of Catostomus commersonii (Lacépéde). Finally, Lithe’s (1910) characterization of the family will have to be slightly emended to include this new species: CARYOPHYLLAEIDAE Liihe 1910, e.p. Monozootic pseudophyllidea with scolex unarmed; may or may not bear more or less well expressed sucking organs which are set off from the rest of the body by a neck- like constriction or are fused with the same without such. A caudal appendage bearing on its hinder end the hooks of the oncosphere may also be present in the sexually mature animal. Genital organs present only singly. Reproductive openings surficial, ventral, medial and near the posterior end. Testes, numerous, exclusively anterior to the ovary and the female genital ducts. Cirrus unarmed, ahead of the female sexual apertures; vagina and uterus open at the bottom of a common vestibule which resembles in its histological structure the shallow genital atrium and opens into it close behind the cirrus. Ovary two-winged, directly behind the genital opening. Vitelline follicles in the medulla, but peripheral to the testes and more or less completely surrounding them like a mantle; mostly ahead of the ovary, but a group also in the hinder end of the body, separated from the main mass by the ovary and the female genital ducts. Uterus a winding canal, without sack-like expansions. Eggs, operculate. College of Medicine, University of Illinois. GLARIDACRIS CATOSTOMI GEN. NOV., SP. NOV. 23 WORKS CITED Cooper, A. R. 1919. North American Pseudophyllidean Cestodes From Fishes. Ill. Biol. Monogrs., 4:289-541, 13 pls. FRAIPONT, J. 1880. Recherches sur l’appareil excréteur des trematodes et des cestodes. Arch. Biol., 1:415-36, 2 pls. Ltue, M. 1910. Parasitische Plattwiirmer. II Cestodes. Die Siisswasserfauna Deutsch- lands, Dr. Brauer, Berlin, Heft 18:1-153. MonrvIceEttl, F. S. 1892. Appunti sui Cestodaria. Atti d. r. accad. sc. fis. mat. di Napoli, 5, ser. 2(6), 11 pp., 4 figs. MrAzek, A. 1908. Ueber eine neue Art der Gattung Archigetes. Vorliufige Mittheilung. Centrbl. Bakt., Orig., 46:719-23. SAINT-Remy, G. 1890. Recherches sur la structure des organes genitaux du Caryophyllaeus muta- bilis Rud. Rev. biol. du nord de la France, Lille, 2:249-60, 1 fig. SCHNEIDER, G. 1902. Caryophyllaeus fennicus n. sp. Arch. Naturgesch., 68J, 1:65-71, 82-98, 3 figs. SKRJABIN, K. 1913. Fischparasiten aus Turkestan. I. Hirudinea et Cestodaria. Arch. Naturgesch., 79J, Abt. A, 2:2-10, 2 pls. STEUDENER, F. 1877. Untersuchungen iiber den feineren Bau der Cestoden. Abhandl. naturf. Gesellsch., Halle, 13:277-316, pls. 28-31. Warp, H. B. 1911. The Discovery of Archigetes in America, with a Discussion of its Structure and Affinities. Science, N.S., 33:272. Warp, H. B. and G. C. WurepLe, 1918. Fresh-Water Biology. New York. WI, H. 1893. Anatomie von Caryophyllaeus mutabilis Rud. Ein Beitrag zur Kenntnis der Cestoden. Zeitschr. wiss. Zool., 56:1-39, 2 figs., 2 pls. Wricat, R. R. and A. B. Macatium, 1887. Sphyranura osleri: a contribution to American helminthology. Journ. Morph., 1:1-48, 1 pl. EXPLANATIONS OF FIGURES co cirrus opening g glands cs Cirrus-sac ~ isthmus of ovary ev excretory vessel Im longitudinal muscles fa female atrium , n nerve(s) ns nerve strand Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Tig. Fig. Fig. Fig. Fig. Fig. A. R. COOPER ovary t testis outer longitudinal muscles u uterus renal cell v vagina shell-gland vf _ vitelline folliscles vs vesicula seminalis Unless otherwise stated, the lines indicating the magnifications of the figures are 0.5mm. in length. Fe eh ee os oa PLATE I Surficial view of scolex of specimen 3.5mm. in length. Lateral view of same. Surficial view of scolex of specimen 21mm. in length. Lateral view of same. Scolex of Archigetes brachyurus, surficial view. After Mrazek. Genital organs in posterior end of worm, toto preparation, surficial view. Pits in the mucosa of the host’s intestine, each showing only two of the several larvae found in them. 8. A terminal renal cell and its connections, from a frontal section. The line at the side represents 0.05mm. o 10. an 12e 13. 14. PLATE IT Transection thru the middle of the scolex. Transection thru the anterior part of the neck. Transection thru about the middle of the whole worm. Transection thru the cirrus-sac. Transection thru the ovarian isthmus. Three stages in the development of the vitelline cells: a, the primordial cell from the periphery of the follicle; b, an intermediate stage from the centre of the follicle; c, the mature cell from the vitelline reservoir. The line repersents 0.02mm. Fig. 15. The smallest larvae procured. TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XXXIX ee Bs. 2 PLATE I COOPER “— TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XX XIX PLATE II COOPER > wh, a , t 3 Y My ee Ps 7 . " ’ ciZ * 4 eee 2 en as 4 c , dug oer) Ss 2 ; : iy, rl e. ‘ 7 ! y f i) at i . i ; rc orw J a¥ A ¢ G yea \ footy / A w ' ‘ ina r * A a - THE GENERA OF THE EN CHYTRAEIDAE (OLIGOCHAETA)! By Paut S. WELCH INTRODUCTION Michaelsen’s monograph (1900) on the Oligochaeta contains the last general revision of the genera of the Enchytraeidae for the whole world. Eisen (1905) modified, to some extent, the genera then known to occur in North America. Since the publication of the above-mentioned works numerous contributions to the knowledge of these annelids have been made, so that the family has grown from a relatively small group containing 13 genera and less than 100 species to the present status of 16 genera and approximately 325 species. With this marked increase has come the necessity for certain changes and modifications in the limits of most of the groups. The revision herein presented is the direct result of the discovery of certain enchytraeids which failed to agree exactly with any of the older generic descriptions and in order to properly assign them a careful survey of several genera was necessitated. It was then decided to extend the study to include all of the known genera of Enchytraeidae and thus not only make available a considerable amount of inaccessible material but also present something which will serve as a basis for further revision as soon as more data are secured. The writer wishes to acknowledge indebtedness to one of his graduate students, Miss Helen M. Scott, who gave considerable assistance in testing and rechecking the revised generic descriptions. This revision can at best be regarded only as an attempt to indicate progress to date. Certain unsurmountable difficulties make it impossible at the present time to do more than work over critically the published records as they now stand and to determine the present status of each group as nearly as possible. The descrip- tions of all of the species now assigned to the Enchytraeidae (approxi- mately 325) have been re-examined in this connection and the work of the writer on this group of annelids, covering a period of ten years, has been brought to bear upon the task wherever possible. The ‘ Contribution from the Zoological Laboratory of the University of Michigan. 25 26 PAUL S. WELCH principal difficulties are indicated below in order to point out some of the features which should receive attention in future investigations and revisions: 1. Descriptions based upon sexually immature specimens or upon material not so stated but apparently immature. 2. Species placed tentatively in certain genera but data insuff- cient to make final disposal of them. 3. Lack of information on morphological features now known to have important systematic value, especially in the older descriptions 4, Deviations which strongly have the appearance of being errors of observation or of printing. 5. Structures recorded as “‘not seen” or “not found” sometimes the result of faulty methods of study, such as external examination only or dissection only, or the use of poorly preserved specimens. 6. Difficulty in correct interpretation of certain descriptive terms, as for example, does “lobulated testes’? mean divided testes as repre- sented in Lumbricillus or something much less significant. In the absence of illustrations which supplement the descriptions, such expressions are very puzzling. 7. Interpretation of indefinite terms indicating differences of degree, as for example, “‘setae slightly curved,” an expression which when unaccompanied by further explanation or by figures is practically unusable. 8. Difficulty arising from descriptions which fail to mention important organs. Does lack of mention always or ever mean posi- tive absence of the structure? Apparently, many investigators have not realized the importance of stating positively that certain charac- ters are absent. To leave these matters without mention is a distinct detriment. In this revision, the generic descriptions have been so modified as to include what seems to be well founded changes demanded by in- creased data as well as new features now regarded as having generic value. In making these modifications the procedure has been as follows: 1. The writer concurs with those who hold that the multiplication of genera should be avoided except where the case is perfectly clear. 2. Genera and species founded upon sexually immature material have been disregarded. It is well established that complete, depend- THE GENERA OF THE ENCHYTRAEIDAE 27 able data cannot be secured from immature specimens and it is to be hoped that future investigation will frown upon any disposition to write descriptions from such imperfect material. It can only lead to confusion and hinderance. 3. Data easily derivable from illustrations not supplemented by description were regarded as valid. 4. Lymphocytes and the brain have been omitted purposely from generic consideration since the writer doubts their value in generic distinction. 5. In certain cases, statements known to be true for some of the species of a genus have been incorporated in the generic description since they represent all that is known at present about the features mentioned. Re-examination of the other species will decide whether such features will remain valid. 6. When the usual generic characters are not mentioned in the descriptions, such omission is taken to mean that no information is available, rather than that they are absent. 7. There have been incorporated into the genus descriptions certain features which may prove later to be specific characters, as for example, when structures are indicated as “‘present and absent.” This is done largely for the sake of record and to indicate divergences from the former descriptions. It remains for future investigation to make the final disposal. 8. The term chylus cell is used to indicate the large, intestinal cells each of which is characterized by a longitudinal, intracellular canal. In the region involved, chylus cells usually alternate with the ordinary epithelial cells which line the lumen of the intestine. 9. Eisen’s system of classifying the various forms of penial bulb has been followed to considerable extent. There is increasing evidence that the features of the penial bulb have distinct generic value. 10. No attempt has been made to list more than the most impor- tant literature involved in making this review. A complete set of references and a statement of the synonymy up to 1900 is given in Michaelsen’s monograph. SUBFAMILIES Some attempts have been made in the past to establish sub- families in the Enchytraeidae. Eisen (1905, pp. 11-13) proposed 28 PAUL S. WELCH four subfamilies, Mesenchytraeinae, Enchytraeinae, Achaetinae, and Lumbricillinae, the major basis of distinction being the character of the penial bulb. However, since the structure of the penial bulb was not known for certain genera, the distribution of the genera among these subfamilies was to some extent inferential. Cejka (1910, p. 25) made use of three subfamilies under the names Frideri- citinae, Mesenchytraeinae and Henleinae. There seem to be some good grounds for considering the structure of the penial bulb as a basis for the erection of subfamilies, but since its structure is unknown in such genera as Achaeta, Distichopus, Chirodrilus, and Stercutus, it does not seem profitable just now to attempt to discuss this problem. THE PENIAL BULB The first attempt to use the characters of the penial bulb in the classification of the Enchytraeidae was made by Eisen (1905, pp. 6-10) who, after an extensive study of a large number of North American species, thought it possible to recognize three distinct “types” which were definitely related to certain taxonomic groups. The writer (Welch, 1914, pp. 173-180) presented a critical discussion of this matter, pointing out that it seemed necessary to make some modifications in Eisen’s original system. Since that time many more of the North American forms have been studied and while it is still probable that certain changes may ultimately be necessary, all of the evidence at hand indicates that the characters of the penial bulb are valuable in generic and possibly in specific diagnoses. For this reason, statements as to the penial bulb have been incorporated into revised definitions of the various genera, retaining Eisen’s terms for the different types. If many of the species from the Old World can be re-examined and the structure of the penial bulb described and figured, the taxonomic status of this organ will be made more certain. For sake of ready reference, Eisen’s summary of the three types of penial bulbs will be quoted here. “The Meseéenchytreid bulb is a single muscular structure, con- taining circular muscles as well as fan-shaped muscular bands connec- ting the body wall with the periphery of the bulb. Between the muscular bands are generally found numerous penial glands which THE GENERA OF THE ENCHYTRAEIDAE 29 open on the surface of the bulb around the penial pore. The sperma- duct penetrates the bulb, opening on the center of its outer surface. The Enchytreid bulb is multiple, consisting of several separate cushions grouped around the penial pore. In these cushions we find several sets or fascicles of glands, each fascicle opening by itself on the surface of the body. There are no muscular bands connecting the base of the cushions with its periphery. The sperm-duct never penetrates the bulbs or cushions but opens close to and independently of them. Exterior to the cushions there are numerous muscles connecting the body wall immediately surrounding the pore with other parts of the same somite. The Lumbricillid bulb is always single and covered with a strong muscular layer, which however never penetrates down between the cells of the bulb. There are generally two or three distinct sets of glandular cells in the bulb. Some of these open in the lower part of the sperm-duct, or rather in a narrow groove in the elongation of the sperm duct. Others open on the free surface of the bulb, either irregularly or in narrow circular fields, bunched into fascicles. The sperm-duct penetrates one side of the bulb. In Bryodrilus the gland which opens in the extension of the sperm-duct is covered with a thin cushion of muscular strands, forming a bulb within a bulb.”’ RELATIONSHIPS It is not intended that any particular significance be attached to the order in which the different genera are treated in this paper. Certain genera are too poorly known at present to justify any attempt to establish relationships, while others are little enough known to make it a difficult and an uncertain task. It thus seems best in this paper to omit efforts to determine phylogeny. PROPAPPUS MICHAELSEN Setae sigmoid; distal extremity cleft; those of a bundle equal; four bundles per somite, two lateral and two ventral. Dorsal pores absent. Oesophagus passing abruptly into intestine in 8; intestinal diverticula absent; chylus cells absent; peptonephridia absent. Origin of dorsal blood-vessel anteclitellar or intraclitellar. Nephricia with small, slender, funnel-shaped anteseptal part and with loose, scantily lobed, irregularly folded postseptal body, the folds being but 30 PAUL S. WELCH little more than in close contact. Testes undivided; moderately compact. Spermiducal funnel extremely short; shallow bowl-shaped. Sperm duct very short; confined to 12. Penial bulb absent; small atrial chamber at ectal end of sperm duct; atrial glands absent. Spermathecae simple; no diverticula; no connection with digestive tract; long, extending into 6-12. DISCUSSION Formerly, the genus Henlea (Michaelsen, 1903, p. 51) was re- garded as the most primitive group of the Enchytraeidae because of the diverse character of the setae manifested by the various species although it presented no distinct transition features leading into the near-standing, more primitive families of Oligochaeta (Phreodrilidae, Tubificidae, Naididae). In 1905, however, Michaelsen (pp. 24-28) described under the name Propappus a genus based upon specimens found abundant in Lake Baikal, Southern Siberia, at depths of 2-8 meters. These specimens presented a complex of characters of par- ticular interest. Most of the fundamental features are enchytraeid leaving little doubt as to its membership in that group. However, certain affinities with other families are manifested in the presence of the following structures: 1. Cleft setae are recorded for the first time among the Enchy- traeidae, all other known species having the simple-pointed type. Cleft setae are common in Naididae, Tubificidae, and Lumbriculidae. 2. The spermiducal funnel is a very short, shallow, bowl-shaped organ, resembling the funnel in certain other oligochaetes (Tubéfex, et al) and showing little resemblance to the elongate, cylindrical, glandular, thick-walled funnel found in practically all enchytraeids. Apparently, only two other enchytraeids have spermiducal funnels which at all resemble those of Propappus, namely, Mesenchytraeus bunget Mchlisn. and Mesenchytraeus grebnizkyi Mchlsn. (Michaelsen, 1901, pp. 193, 199), in which they are very short, and ‘“‘pantoffel- formig.”’ 3. Each nephridium consists of a small, slender, funnel-shaped nephrostome which constitutes the entire anteseptal part. The postseptal part, however, departs strikingly in form and structure from the typical enchytraeid condition in being very loosely con- structed, having the appearance of an irregular knot of adherent loops THE GENERA OF THE ENCHYTRAEIDAE 31 or folds, the free end of which composes the efferent duct. This type of nephridium recalls the postseptal coils in the same organ in Tubificidae, et al. Of all the other enchytraeids, Mesenchytraeus alone shows any approach to such nephridial structure, although its irregular, lobed, postseptal part in which the wide ducts are close together is definitely coalesced into one mass. Only two species are known at present to belong to this annectent genus, namely, glandulosus and volki. The former, found in Lake Baikal, in the one on which the genus was established. Recently, Michaelsen (in a paper dated 1915 but which must have been pub- lished in 1916 since papers dated 1916 are referred to in it) described a second species, volki. It appears that this same writer first reported it in the “Hamburger Nachrichten, Jahrg. 1916, Nr. 53, vom 30, Januar, 3. Beilage, p. 1,” as Palpenchytraeus volki, n. gen., n. sp. but later placed it in Propappus—a decision which certainly seems more nearly correct. It is worthy of mention that in this species the elongated spermathecae recall the condition in many of the North American mesenchytraeids. HENLEA MICHAELSEN Setae straight and unequal in size, or straight and equal in size, or slightly sigmoid and approximately equal in size; distal extremities simple-pointed; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent. Oesophagus (with possible rare exceptions) expanding abruptly into intestine. Peptonephridia present or absent. Intestinal diverticula usually present. Origin of dorsal blood-vessel anteclitellar; rarely intraclitellar; cardiac body absent. Blood colorless. Nephridia with either large or small ante- septal part; nephridial canal loosely wound and surrounded by con- siderable amount of cell mass. Ventral glands absent. Testes com- pact; not divided. Spermiducal funnel cylindrical; sperm duct short, confined to 12, rarely longer. Sperm sacs and ovisacs absent. Penial bulb of lumbricillid type. Spermathecae connecting with digestive tract; diverticula present or absent. DISCUSSION Perhaps no genus of Enchytraeidae needs a thorough going revi- sion as badly as does Henlea. Its heterogeneous nature has been a2 PAUL S. WELCH recognized by investigators for some time but certain conditions surrounding the problem have thus far made such a revision almost impossible. It therefore presents many difficulties in connection with the present attempt to redefine the genus. Friend (1914b, pp. 150-153; 1915, pp. 197-198) has pointed out the existence of certain “groups”? within this genus. The writer [Welch] suspects strongly that Hepatogaster Cejka should be regarded as a part of the genus Henlea—possibly as a subgenus. It seems likely that these “groups” will form the basis for the establishment of several sub- genera when the genus is thoroughly worked over, particularly when many of the foreign species have been re-examined and more thoroughly described. Certain deviations, apparent or otherwise, from the newly modi- fied genus definition require some notice. Some ill-defined species (lefroyi Beddard; scharfii Southern; et al) seem to offer exceptional features, but the imperfect descriptions leave considerable doubt as to whether they belong in this genus at all. Hence no significance can be attached to them at present. Eisen (1905, p. 98), in connection with his discussion of Henlea, presents the following statement: ‘‘Chylus cells in the intestine in the vicinity of clitellum.’’ However, in his subsequent descriptions, no mention of them appears except in the case of H. guatemalae (pp. 102-103) which is described as having no chylus cells at all. In none of the American species of Henlea examined by the writer have chylus cells been observed. A number of species have been described in which the origin of the dorsal blood-vessel is specified as intraclitellar and the definition has been modified so as to include these forms. However, Friend (1913b, pp. 460-461) has described a species under the name insulae which has the dorsal blood-vessel arising in ‘117/18 or 19/20.” This form is assigned to Henlea but taking the original description as it stands, the writer is unable to place it with any more certainty in Henlea than in one or two other genera, as for example, Enchytraeus. For this reason, the apparent exception has not been given any particular consideration. H. alba (Friend, 1913c, p. 83) and H. hillmani (Friend, 1914b, p. 135) are reported as having the origin of the dorsal blood- vessel in'the region of 13-14. THE GENERA OF THE ENCHYTRAEIDAE oo Of the sixty or more species now assigned to this genus, there are several which future investigations will certainly prove invalid. HEPATOGASTER CEJKA Setae straight and equal; distal extremities simple-pointed; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent. Oesophagus merging gradually into intestine. Peptonephridia present, dorsal and ventral. Intestinal diverticulum present, surrounding digestive tract. Chylus cells absent. Origin of dorsal blood-vessel anteclitellar; cardiac body absent. Nephridia with smaJ] anteseptal part; nephridial duct loosely coiled and with distinct cell mass. Testes not divided. Spermiducal funnel cylindri- cal. Penial bulb of lumbricillid type. Spermathecae connecting with digestive tract; diverticula absent. Characteristic, longitudinal canals in epithelium of digestive tract in posterior part of body just entad of perivisceral blood-sinus. DISCUSSION The genus Hepatogaster was established by Cejka (1910) for the reception of two species which he considered as presenting characters representing a new group. A careful examination of descriptions reveals at least a close affinity with Henlea. In fact, it could be included in Henlea with practically no change in the limitations of the latter. Only one feature seems to offer any difference, namely, that the oesophagus passes gradually into the intestine, but it seems doubtful if a new genus could be established upon that character alone. The presence of certain peculiar longitudinal canals in the epithelium of the posterior part of the alimentary canal is stressed in the original description and while these characters seem to be unique, their value as a generic character remains to be demonstrated. The structure of the penial bulb requires some notice. Cejka thought that it resembled the enchytraeid type, interpreting certain peculiar glands which open out through the body-wall in 12 and 13 in the vicinity of the sperm duct termination as parts of the penial bulb proper. Unfortunately, the penial apparatus is recorded in only one of the two species. However, a careful study of the description and Cejka’s plates leads the present writer to hold that the bulb is of the lumbricillid type for the following reasons: 1. The sperm duct opens 34 PAUL S. WELCH to the exterior through a compact, glandular bulb which is typically lumbricillid. This duct actually opens out through it into a penial invagination—a thing which does not occur in the typical enchytraeid bulb. (2) Of the nearby groups of problematical glands, the one in 12 is single and median, thus apparently belonging to neither bulb. (3) The other glands are in 13—another somite—a thing which has not been observed in connection with the various parts of a typical enchytraeid bulb. (4) In general appearance these peculiar glands resemble the ‘‘ventral glands” found in certain enchytraeids although they are unusual in being free from direct connections with the ven- tral nerve cord. Owing to the incompleteness of some of the data on this proposed genus, it is allowed to stand for the present although there seem to be good reasons for believing that it should be reduced at least to the rank of a subgenus of Henlea. ~ BRYODRILUS UDE Setae slightly or distinctly sigmoid; distal extremities simple- pointed; those of a bundle equal in size; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent. Oesophagus merging gradually into intestine. Peptonephridia pre- sent. Four intestinal diverticula present. Origin of dorsal blood- vessel intraclitellar; cardiac body present or absent. Nephridia with small anteseptal part; nephridial canal loosely wound; cell mass large. No ventral glands. Testes compact; not divided. Spermiducal funnel cylindrical; sperm duct confined to 12. Sperm sacs and ovisacs absent. Penial bulb of lumbricillid type. Spermathecae connecting with digestive tract; diverticula absent. DISCUSSION While a few slight modifications have been introduced into the description of this genus, no important comments are demanded here. No mention of intestinal diverticula appears in the description of B. sulphureus (Bretscher, 1904, p. 262) but since the material on which the description was based was immature, this omission may have no significance. The head pore in this same species is recorded as appearing on the tip of the prostomium. Four species are assigned to this genus. THE GENERA OF THE ENCHYTRAEIDAE 35 BUCHHOLZIA MICHAELSEN Setae sigmoid; distal extremities simple-pointed; those of a bundle approximately equal in size; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent. Oesophagus expanding abruptly into intestine. Peptonephridia present. Chylus cells absent. Origin of dorsal blood-vessel anteclitellar or intraclitel- lar; arising from summit of dorsal intestinal diverticulum; cardiac body absent. Blood colorless. Nephridia with anteseptal part large or small. Spermiducal funnel cylindrical; sperm duct confined to 12. Structure of penial bulb unknown. Spermathecae connecting with digestive tract; diverticula absent. DISCUSSION In Buchholzia focale (Friend, 1914a, pp. 118-119) no mention is made of a dorsal intestinal diverticulum and the origin of the dorsal blood-vessel is given as ‘‘Henlean.”’ But little is known concerning the penial bulb in representatives of this genus. Eisen (1905, p. 12) places the genus under his sub- family Lumbricillinae but explains (p. 6) that he does so on account of its ‘undoubted relationship to the genus Henlea.”’ Buchholzia parva (Bretscher, 1900a, p. 24) is described as showing no connection of the spermathecae with the digestive tract. However, the sexual maturity of the material might be questioned since it is stated that no trace of a clitellum was found. Six species are now assigned to this genus. MARIONINA MICHAELSEN Setae sigmoid; distal extremities simple-pointed; those of bundle approximately equal in size; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent. Oesophagus merging gradually into intestine. Peptonephridia absent. Intestinal diverticula absent. Chylus cells absent. Origin of dorsal blood- vessel postclitellar; cardiac body absent. Blood red, yellow, or color- less. Nephridia with anteseptal part large or small; nephridial canal loosely wound; cell mass large. Ventral glands present or absent. Testes undivided. Spermiducal funnel cylindrical; sperm duct con- fined to 12. Sperm sacs present or absent. Penial bulb of the lumbri- 36 PAUL S. WELCH cillid type. Spermathecae with or without connection with digestive tract; never greatly elongate; diverticula present or absent. DISCUSSION In a few species, assuming that they are correctly referred to this genus, there seems to be some deviation as to the origin of the dorsal blood-vessel. Bretscher (1900b, p. 449; 1901, pp. 209-10) described rivularis and guttulata as having this origin anteclitellar, and Eisen (1905, p. 91) reported it in 12 in the single specimen of alaskae which he described although he retained the general generic character of a postclitellar origin (p. 90). Friend (1912a, p. 224) has described a species, sialona, which he assigns to Marionina, pointing out at the same time that it is striking- ly like an Enchytraeus. ‘This species possesses peptonephridia—a feature not represented in Marionina and sialona is unique in that respect if it actually belongs in Marionina. However, the writer has been unable, on the basis of the original description, to see why that species should not be assigned to Enchytraeus, rather than to Marion- tna. If this be the proper disposal of sialona, then the absence of peptonephridia still stands as an invariable character of the genus. Eisen (1905, p. 90) held that a generic character appears in the presence of a small sperm sac in connection with each testis. Whether this is true, remains to be determined by future investigations. In antipodum (Benham 1904b, p. 294) the body of the penial bulb appears to be of the lumbricillid type, but it is unique in possess- ing a single, large accessory gland. Bretscher (1901, p. 210) recorded guttulata as “‘ohne Prostata,’ but the whole description is so brief that it is impossible to judge accurately as to the sexual maturity of the material studied, or as to the exact meaning of the above quoted statement. M. werthi Mchlsn. (1908, p. 15) has a penial bulb which is de- scribed as ‘‘einen winzigen, zwiebelférmigen, ganz in der Leibeswand verborgenen Bulbus aus. An diesen Bulbus, der manchmal als winzige diussere Papille etwas heraustritt, sitzt eine schwach gelappte, in die Leibeshéhle hineinragende Prostata.” About twenty-eight species are referred to this genus. THE GENERA OF THE ENCHYTRAEIDAE 37 LUMBRICILLUS ORSTED Setae sigmoid; distal extremities simple-pointed; those of a bundle approximately equal in size; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent. Oeso- phagus merging gradually into intestine. Peptonephridia absent. Intestinal diverticula absent. Chylus cells absent. Origin of dorsal blood-vessel postclitellar, rarely intraclitellar; cardiac body absent. Color of blood yellow, red, or colorless. Nephridia with anteseptal part either large or small; nephridial canal loosely wound, and con- siderable cell mass between the folds. Ventral glands present or absent. Testes divided deeply, forming a number of distinct lobes. Spermiducal funnel cylindrical; sperm duct long but confined chiefly to 12. Sperm sacs and ovisac absent. Penial bulb of lumbricillid type. Spermathecae connecting with digestive tract; diverticula absent. DISCUSSION While the limits of this genus have been but little changed, certain variations may well be mentioned here. L. viridis (Stephen- son, 1911, p. 48) has the dorsal blood-vessel arising in 13 and in ¢uba (p. 43) it arises in 13, 14, 15. A variety (?) of minutus (Miill.) described by Michaelsen (1911, pp. 1-4) has this vessel arising in 12. Lineatus (Miill.) (=agilis Moore) has also been described by some authors as having the dorsal vessel arising in 13. Ventral glands do not appear in all representatives of Lumbricil- Jus. Furthermore, they are said to occur in a few species of certain other genera (Welch, 1914, p. 141). Distinct sperm sacs and ovisacs appear to be absent in this genus. A few references to very diminutive ovisacs restricted to the clitellar region occur in the literature (Eisen, 1905, p. 77; Moore, 1905, p. 397) but these can scarcely be regarded as having any special signifi- cance. Eisen (1905, pp. 75-76) stated that each division of the testes is capped by a small sperm sac and evidently regarded this as a generic character. Stephenson (1911) has pointed out the close relation of Lumbricil- lus to Enchytraeus on the basis of the discovery of certain species which though assigned to the former, possess some characters strongly suggestive of the latter. 38 PAUL S. WELCH About thirty species are assigned to this genus at present, although there is reason for doubting the validity of some of them. FRIDERICIA MICHAELSEN Setae straight or nearly so; unequal, those in bundle developed in pairs, outer pair being largest, and enclosing smaller pairs; distal extremities simple-pointed; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores present. Oesophagus merging gradually into intestine. Peptonphridia present. Intestinal diverticula absent. Chylus cells present. Origin of dorsal blood- vessel postclitellar or intraclitellar, usually the former; cardiac body absent. Blood colorless. Nephridia usually with large anteseptal part, always consisting of more than nephrostome; cell mass well developed. Ventral glands usually absent. Testes not divided. Spermiducal funnel cylindrical; sperm duct short, usually confined to 12. Sperm sacs and ovisacs absent. Penial bulb of lumbricillid type. Spermathecae usually connecting with digestive tract; diver- ticula present or absent. DISCUSSION While it seems advisable to make but little modification in the description of Fridericia, a few variations as recorded in the literature demand notice here. F. tusca and F. valdarnensis are described by Dequal (1914, pp. 15,17) as having setae which are sigmoid but those of a bundle are of unequal length, the inner ones being shorter. The description is very meager but it appears that even though they be sigmoid, they still resemble the typical Fridericia arrangement and development. Stephenson (1915, p. 47) describes the setae of F. carmichaeli as being of the “Enchytraeus type’? but it may be that since in this species there are usually only two setae per bundle and since the outer setae of a Fridericia bundle are straight and approximately the same size, this statement could be true, although if more were present per bun- dle the inner ones might be shorter, smaller, and arranged in pairs. Friend (1912b, p. 24) states that the head pore in F. anglica occurs on the tip of the prostomium. In Fridericia peruviana, Friend (1911, pp. 734-736) described the oesophagus as passing abruptly into the intestine, but since the specimens on which the description was based THE GENERA OF THE ENCHYTRAEIDAE 39 were immature, it seems best to attach no particular significance to this case. According to Southern (1909, p. 165) F. magna Friend has bright red blood. Friend (1899, p. 263) stated that in F. magna an ovisac is present, extending caudad to 16. At present about 90 species are assigned to Fridericia and while it is very possible that some of them are not valid, it appears that this is the largest of all the enchytraeid genera. DISTICHOPUS LEIDY Setae in two bundles per somite, representing the ventral rows only; nearly straight; simple-pointed but blunt; very stout and swollen in middle; hooked at proximal end. Head pore at 0/1. Oesophagus merging gradually into intestine. Peptonephridia present. Origin of dorsal blood-vessel postclitellar; small cardiac body present. Blood colorless. Nephridia with small anteseptal part. Spermiducal funnel cylindrical; sperm duct short, confined to 12. Penial bulb of lumbricillid type. Spermathecae not described. DISCUSSION The genus Distichopus is known only from a single set of specimens collected in Delaware and Pennsylvania by Leidy (1882, pp. 146-147). Some of these specimens were later studied by Moore (1895, pp. 754-756) who extended the account, although even yet too little is known concerning this unusual form. Certain important structural features, such as the spermathecae, are yet undescribed and thus the relationships of this genus are difficult to determine. Moore holds that it is a close ally of Fridericia. The single known species bears the name silvestris. ACHAETA VEJDOVSKY Setae entirely absent; dorsal and ventral rows preserved in some species only as pear-shaped gland cells in body-wall, gland cells also absent in other species. Head pore large; on tip of prostomium.. Dorsal pores absent. Oesophagus merging gradually into intestine. Peptonephridia present or absent. Origin of dorsal blood-vessel anteclitellar. Blood colorless. Nephridia with moderate or large anteseptal part. Spermiducal funnel cylindrical; sperm duct short or long but confined to region of clitellum. Penial bulb present; struc- 40 PAUL S. WELCH ture practically unknown; probably of lumbricillid type. spermathe- cae with or without connection with digestive tract; diverticula absent. DisSCUSSION Achaeta is a small genus to which is assigned, at the present time, eight species, none of which occur in the Western Hemisphere. Its most striking characteristic is the total absence of setae. In most of the species, specialized, pear-shaped seta-glands occur in the positions where setae would be expected, although three species, veydovskyi Bretscher (1902, p. 27), maorica Benham (1904a, pp. 221— 223) and camerani (Cognetti 1899, pp. 1-4) are described as being completely devoid of seta-glands. Peptonephridia have not been found in minima Southern (1907, p. 77) and incisa Friend (1914b, pp. 133-134) but occur in the other known species. The penial bulb is practically unknown for this group since in no case is it described in adequate detail. It was figured by Vejdovsky (1879, pl. I, fig. 11) for eisenit but even there it is difficult to determine its exact composition. It suggests the lumbricillid type of bulb. In maorica Benham (1904a, p. 222) the spermathecae are greatly elongated, extending to 9 or 10, thus recalling the greatly elongated spermathecae of some of American species of Mesenchytraeus. ENCHYTRAEUS HENLE Setae straight; those of a bundle equal; distal extremities simple- pointed; four bundles per somite, two lateral and two ventral. Head pore at 0/1. Dorsal pores absent; Oesophagus merging gradually into the intestine. Peptonephridia present or absent. Intestinal diverticula absent. Chylus cells absent. Origin of dorsal blood- vessel postclitellar or intraclitellar; cardiac body absent. Blood usually colorless. Nephridia with small anteseptal part; cell mass well developed. Ventral glands sometimes present. Testes not divided. Spermiducal funnel cylindrical; Sperm duct confined to 12, or quite long, extending caudad through several somites. Sperm sacs present or absent. Penial bulb of enchytraeid type. Sperma- thecae connecting with digestive tract; diverticula present or absent. THE GENERA OF THE ENCHYTRAEIDAE 41 DISCUSSION While it has been necessary to modify the older definition of the genus, only a few points require mention here. E. dubius (Stephen- son, 1911, p. 56) is unique in possessing testes which are divided very much as is the case in representatives of the genus Lumbricillus. However, Stephenson himself (1915, p. 43) indicates that there is some doubt as to the generic position of this species. The same writer (1915, pp. 43-44) gives a critical discussion of sperm sacs in the genus Enchytraeus but makes no attempt to draw a general conclusion. Since the matter of sperm sacs is still in doubt, it seems best, in this paper, to use the data directly from the original descriptions and consider the statements of absence of sperm sacs as valid until they are definitely shown to be in error. The writer (Welch, 1914, pp. 177-178) previously discussed the penial bulb as a generic character and pointed out that not all of the species included in Enchytraeus conform to the enchytraeid type of bulb. However, it appears at this time. that in the cases in which the penial bulb has been adequately described the large majority have bulbs of the enchytraeid type as proposed by Eisen and may so be incorporated into a revised state- ment of the limits of the genus, at least until subsequent investigation yields more complete data. Eisen (1905, p. 61), in his generic description, states that the intes- tine generally possesses chylus cells. However, no mention of these cells is made later in his descriptions of species. A genus, Litorea, described by Cejka (1913) for the reception of a species which he called krumbachi, is certainly the same as Enchytraeus and is so treated in this paper. About thirty-five species are considered as belonging to this genus at the present time. MICHAELSENA UDE Setae straight; distal extremity simple-pointed; one to two setae per bundle, often but one; four bundles per somite, two lateral and two ventral; present only on some of the somites (except in M. man- gert Mchlsn.). Head pore at 0/1. Dorsal pores absent. Oesophagus merging gradually into intestine. Peptonephridia present or absent. Intestinal diverticula absent. Origin of dorsal blood-vessel post- clitellar; cardiac body absent. Blood colorless. Nephridia with 42 PAUL S. WELCH small anteseptal part, consisting of nephrostome only. Ventral glands absent. Testes not divided. Spermiducal funnel cylindrical; sperm duct confined to 12, or long and extending caudad to 14. Penial bulb of the enchytraeid type. Spermathecae connecting with diges- tive tract; diverticula absent. DISCUSSION Formerly the absence of setae from some or the majority of the somites was regarded as one of the chief distinguishing features of this genus but Michaelsen (1914, pp. 177-181) described a new species under the name mangeri in which setae are present in four bundles on all of the somites. This species may be regarded as a connecting form between Michaelsena and Enchytraeus and at the same time, according to Michaelsen, emphasizes the relation of Michaelsena to Fridericia. Southern (1913, pp. 8-12) described under the name Grania what he regarded as a new genus, pointing out similarities with a form then known under the name of Enchytraeus monochaetus Mchlsn. The latter is now known to belong to Michaelsena and Michaelsen (1914, p. 181) seems to be right in placing Grania there also. Eisen (1905, p. 73) incorporated in his definition of this genus the statement that there are ‘‘No penial bulbs,”’ but this seemed to be based upon the condition which he found in a single specimen to which he gave the name paucispina and which did not permit a full descrip- ctiption. However, the descriptions of species now assigned to Michaelsena indicate that it may be of the enchytraeid type. Eisen (1905, p. 11) placed the genus in his subfamily Enchytraeinae. It seems to be becoming increasingly difficult to separate Michael- sena from Enchytraeus and it is possible that some future revision based upon more intensive study of all of the species involved may suggest the fusion of the two groups. Eight species are assigned to this genus at present. MESENCHYTRAEUS EISEN Setae sigmoid; distal extremities simple-pointed; approximately equal in size in bundle; four bundles per somite, two lateral and two ventral. Head pore distinct; usually at or very near tip of prosto- mium. Dorsal pores absent. Oesophagus merging gradually into THE GENERA OF THE ENCHYTRAEIDAE 43 intestine. Peptonephridia absent. Intestinal diverticula absent. Chylus cells absent. Origin of dorsal blood-vessel postclitellar; car- diac body present. Blood either colorless or red. Nephridia with small anteseptal portion, consisting merely of nephrostome; post- septal part large, irregularly pluri-lobed, and with cell mass between folds of closely wound nephridial canal greatly reduced. Ventral glands absent. Testes compact; undivided. Spermiducal funnel usually cylindrical; sperm duct short and confined to 12, or very long extending caudad for many somites. Sperm sacs and an ovisac often present. Penial bulb of mesenchytraeid type. Spermathecae con- fined to 5, or elongated and extending caudad for varying distances, sometimes to clitellum; diverticula present or absent; communica- tion with digestive tract present or absent. DISCUSSION Eisen (1905, p. 14) stated that a ‘‘single median ovisac” and “‘one pair of sperm-sacs generally of large size’ are present in Mesenchy- traeus. However, Mes. altus Welch (1917, p. 71), which unquestion- ably belongs to this genus, has a pair of ovisacs and it seems possible that other cases of that sort will appear. Several special cases which depart somewhat from the definiton as proposed require mention here. In eastwoodi Eisen (1905, p. 50) the head pore occurs on the upper side of the prostomium near 0/1. Mes. mencli Vejd. (1905, p. 5) is described as having “‘Herz im 12,” apparently referring to an intraclitellar origin of the dorsal blood-vessel. A similar origin seems true of celticus Southern (1909, p. 155), although the statement is not made positively. Bretscher (1902, p. 16) claimed that specimens of setosus Mchlsn. (=megachaetus Bret.) show the dorsal blood-vessel arising in 11,13, or 16 — which seems an unusual variation. Mes. grandis Eisen (1905, p. 44) is described as having nephridia with broad anteseptal parts. In orcae, mirabilis, and kincaidi (Eisen, 1905, pp. 40-41), the testes are recorded as composed of “lobes” but it is not clear whether they are deeply divided as in the case of Lumbricillus or are merely lobulate at the free extremity. Bretscher (1901, p. 212) states that in alpinus the spermiducal funnel is in 8, but nothing is given concerning the sperm duct. In nanus (Eisen, 1905, pp. 51-52), the penial bulb is described 44 PAUL S. WELCH as absent, but there seems to be some possibility that immature speci- mens were studied. This genus contains at the present time about 50 species. HYDRENCHYTRAEUS BRETSCHER Setae sigmoid; distal extremities simple-pointed; four bundles per somite, two lateral and two ventral. Dorsal pores absent. Oesophagus merging gradually intointestine. Peptonephridia pres- ent. Origin of dorsal blood-vessel postclitellar. Blood yellow or red. Nephridia with large or small anteseptal part. Spermiducal funnel cylindrical. Spermathecae without diverticula. DISCUSSION This genus was established by Bretscher (1901, pp. 208-209) for two incompletely described species, stebleri and nematoides, found in Switzerland. Its status is somewhat uncertain owing to the fact that information on the head pore, relation of oesophagus to intestine, chylus cells, cardiac body, ventral glands, testes, sperm sacs, Ovisacs, penial bulb, and relation of spermathecae to the diges- tive tract is entirely lacking. Likewise certain other features are incompletely described. Since the original description is the only record, nothing further can be done with these forms until specimens are again found and studied critically. The fragmentary information which is available seems to indicate that it is a valid genus. STERCUTUS MICHAELSEN Setae sigmoid; distal extremity simple-pointed; four bundles per somite, two lateral and two ventral. Head pore absent (apparently) or very small. Dorsal pores absent. Oesophagus merging gradually into intestine. Peptonephridia absent. Intestinal diverticula absent. Chylus cells absent. Origin of dorsal blood-vessel anteclitel- lar; cardiac body present. Blood colorless. Nephridia with small anteseptal part consisting of but little more than a mere nephrostome; postseptal part large; nephridial canal loosely wound and surrounded by considerable cell mass. Testes small; undivided. Spermiducal funnel short and distinctly funnel-shaped. Penial bulb unknown. Spermathecae not connected with digestive tract; diverticula absent. THE GENERA OF THE ENCHYTRAEIDAE 45 DISCUSSION The genus Stercutus was established by Michaelsen (1888) to receive a species, zivews, which was found inhabiting fish excrement in Germany. No other representatives of this genus have ever been described. Lack of information as to the character of the penial bulb, the sperm duct, and the presence or absence of ventral glands, Ovisacs and sperm sacs gives some difficulty in determining the affinities of this genus. CHIRODRILUS VERRILL Setae in six bundles per somite, two sub-dorsal, two lateral, and two ventral; those in ventral and lateral bundles distinctly sigmoid, those in sub-dorsal less curved; distal extremities simple-pointed. Blood colorless. DISCUSSION The description of this interesting genus is extremely meager and based entirely upon the original record by Smith and Verrill (1871, pp. 450-451) in which but few of the important details are described. Two species are assigned to this genus, lJarviformis and abyssorum, both collected in Lake Superior. Both are apparently deep water forms, larviformis being dredged from depths of 17 and 59 fathoms, and abyssorum from 47 and 159 fathoms. There is some question as to the position of this genus, certain previous writers having regarded it as a tubificid. Beddard (1895, p. 314) and Michaelsen (1900, p. 88) have classed it among the Enchytraeidae, although the latter (1903, p. 50) later placed it among the Tubificidae. Eisen (1905, p. 13) retains it in the Enchytraeidae. It is unlikely that the matter can receive any positive decision until material is again secured and carefully studied. Since some of the characters as described are apparently enchytraeid in nature, it is included in this review, with the realization, however, that future investigation may show it to have other affinities. If it be an enchytraeid, it is unique for the entire family in possessing six sets of setae per somite. Eisen (1905, p. 13) places it under the Lumbricillinae, but states (p. 6) that it is “appended for convenience sake’’ and points out correctly that nothing is known concerning the penial bulb and other internal structures. 46 PAUL S. WELCH GENERA DUBIA Under the name Chamaedrilus, Friend (1913a, pp. 260-263) described a new genus from material collected in England. Con- sidering the generic characters as recognized at present for the family Enchytraeidae, a careful comparison has made it impossible for the writer to distinguish Chamaedrilus from Marionina and in this paper they are regarded as the same. Bretscher (1905) described what he regarded as a new genus of Enchytraeidae under the name of Euenchytraeus but unfortunately the record was made on sexually immature material and as a conse- quence nothing could be determined as to the nature of the reproduc- tive organs. Since no further record of this postulated genus occurs in the literature and since the original description is unusable as it stands, it is omitted from consideration in this paper. KEY FOR THE IDENTIFICATION OF THE GENERA OF ENCHYTRAEIDAE 1 ( 2) Setae entirely absent; represented in most species only by four longitudinal rows of pear-shaped glands in body-wall STN AER ee a ADEE ERLE CL. = 3 oes) sale Aenean Achaeta 2a): Setae present. 4).'54 8 2k Meee st... 3 3 ( 4) Setae arranged in two bundles per somite...... Distichopus 4 ( 3) Setae arranged in more than two bundles per somite....... 5 5 (6) Setae arranged in six bundles per somite, two subdorsal, two lateral and two ventralereewerme yee... ee! Chirodrilus 6 (5) Setae arranged in four bundles per somite, two lateral and two’ Ventral Ye ener saatieaa ls 6 arc Sten eae 7 7 (8) Setae cleft at distal extremities; spermiducal funnel wide, open, shallow, and extremely short; postseptal part of nephridia composed of a few coherent folds not intimately fused, forming very loose organ...) . .'. ..4c eee Propappus 8 (7) Setae simple-pointed at distal extremities; spermiducal funnel cylindrical or trumpet-shaped; postseptal part of nephridia compact / 2.24.2). i). Pk ee ee 9 9 (10) Setae straight, arranged in pairs, inner pairs of bundle suc- cessively smaller than outer; dorsal pores present; chylus cells: present in* walls of intestine: ... 52/9. seu Fridericia THE GENERA OF THE ENCHYTRAEIDAE 47 10 (9) Setae straight, sigmoid, or in pairs in bundle with smaller ones within; dorsal pores absent; chylus cells absent from WVAIS ONT LESCUME eR UL Ma aN UEN IC en anal ec A ae 11 11 (14) Oesophagus expanding abruptly into intestine........... 12 12 (13) Dorsal blood-vessel arising from anterior end of single, dorsal Intestinal divertiGuUlun ye yy Ie Ne LL Buchholzia 13 (12) Dorsal blood-vessel arising directly from perivisceral blood- BSRATTRS tee ee RUS Uh UN ei CIRO Oe LNRM SOLEMN Rte ty ALN Henlea* 14 (11) Oesophagus merging gradually into intestine............ 15 15 (16) Setae usually absent from several somites (except in Michael- sena mangert Mchlsn.); usually one setae per bundle, never TRAREN ClEAIE DW eel cists ma iaenevs is es eualaancr a yaa) Michaelsena 16 (15) Setae regularly present on all somites except first and last and wossibly Che clicellar is iis Sk Neda NCL MA NI 4 17 MeO) intestinal diverticula present ona 18 18 (19) Setae sigmoid; four distinct intestinal diverticula; origin of dorsal blood-vessel intraclitellar.............. Bryodrilus 19 (18) Setae straight; one intestinal diverticulum completely sur- rounding digestive tract; origin of dorsal blood-vessel ante- Fel] el BEV ROI SP OPS Re SUR tA os NU EA SO AE AN Hepatogaster meen) intestinal diverticula absent...) 2c na le a 21 21 (22) Setae straight; those of a bundle equal........ Enchytraeus POMS EAC GIOMIGIA oe Ua Ne ON uuC A MA lence 23 23°(24) Peptonephridia present..........6053..) Hydrenchytraeus mame) peeptonephridia absent 04). oii.) e owen ae hae a ee 25 25 (26) Origin of dorsal blood-vessel anteclitellar; spermiducal fun- Hempsnort, and trumpet-shaped. 2 )..).305).).)8 0 ue Stercutus 26 (25) Origin of dorsal blood-vessel postclitellar; spermiducal fun- RNR NEIORN CAD G8 UO Uy ailhy eagle u) Wau ia OUi La BGreg 27 Di, ieee Meeecminarite is i MM Sey lr Ai Mls Lumbricillu Za (an enteasonelimotidivideds yee ON in 8 29 29 (30) Cardiac body absent; penial bulb of lumbricillid type; nephridial duct loosely coiled and cell mass of postseptal part well developed; spermathecae never extending through SEVEPAL | SOMMECS HMMs he eis4 aN ALIAS a te Marionina * A few species, e.g., hillmani Fr., insulae Fr., marina Fr., alba Fr., and three or four uncertain forms, have been assigned to Henlea, although they are described as having the oesophagus pass gradually into the intestine. 48 PAUL S. WELCH 30 (29) Cardiac body present; penial bulb of mesenchytraeid type; nephridial duct closely wound and cell mass reduced to mini- PTAA Ss 92 US alo anes ee isccy. cs Sy RN Mesenchytraeus LITERATURE CITED BEDDARD, F. E. 1895. A Monograph of the Order of Oligochaeta. 769 pp., 5 pl. 52 fig. Oxford. BENHAM, W. B. 1904a. Some new species of Aquatic Oligocheta from New Zealand. Proc. Zool. Soc. London, 1903 (Vol. II), pp. 202-232. 3 pl. 1 fig. 1904b. On the Oligocheta from the Southern Islands of the New Zealand Region. Trans. New Zeal. Inst., 37:285-297, 3 pl. BRETSCHER, K. 1900a. Mitteilungen iiber die Oligochaetenfauna der Schweiz. Rev. Suisse Zool., 8: 1-44. 3 pl. 1900b. Siidschweizerische Oligocheten. Rev. Suisse Zool., 8: 435-458. 1 pl. 1901. Beobachtungen iiber Oligocheten der Schweiz. Rev. Suisse Zool., 9:189-223. 1 pl. 1902. Beobachtungen iiber die Oligochéten der Schwiez. Rev. Susse Zool., 10:1-29. 4 fig. 1904. Beobachtungen iiber die Oligocheten der Schwiez. Rev. Suisse Zool., 12:259-267. _ _ 1905. Uber ein neues Enchytraeidengenus. Zool. Anz., 29:672-674. CEJKA, B. 1910. Die Oligochaeten der Russischen in den Jahren 1900-1903 unternom- menen Nordpolarexpedition. I. Ueber eine neue Gattung der Enchy- traeiden, Hepatogaster. Mem. Acad. Imp. Sci. St.-Petersbourg, (8), 29: No. 2, 29 pp. 3 pl. 1913. Litorea krumbachi n. spec. n. gen.—Ein Beitrag zur Systematik der Enchy- traeiden. Zool. Anz., 42:145-151. 10 fig. Cocn_ettI, L. 1899. Descrizione dell’ Anachaeta camerani nuova specie della famigilia degli Enchitreidi. Boll. Mus. Zool. Anat. Torino, 14, Nr. 354, pp. 1-4. DEQUAL, L. 1914. Gli Enchitreidi della Toscana. Monit. Zool. Ital., 25:13-24. 7 fig. EISEN, G. 1905. Enchytreide of the West Coast of North America. Harriman Alaska Expedition, 12:1-166. 20 pl. New York. FRIEND, H. 1899. New British Annelids. Zoologist, (4), 3:262-265. 1911. New British Enchytreids. Journ. R. Micr. Soc., pp. 730-736. 1 pl. 1912a. New British Oligochets. Zoologist, (4), 16:220-226. 1912b. British Enchytraeids. III. The Genus Fridericia. Journ. R. Micr. Soc:, pp: 9-27. THE GENERA OF THE ENCHYTRAEIDAE 49 1913a. British Enchytraeids. V. Species New to Science. Journ. R. Micr. Sac:; pp: 295-271 135 fig: 1913b. Some Jersey Oligochaets. Zoologist, (4), 17:456-464. 1913c. A Key to British Henleas. Zoologist, (4), 17:81-91. 19142. Rare and Unique Sussex Oligochaets. Hastings and East Sussex Natural- ist, 2:114-123. 1914b. British Enchytreids. VI. New Species and Revised List. Journ. R. Micr. Soc., pp. 128-154. 5 fig. 1915. Studies in Enchytraeid Worms. Henlea fragilis Friend. Ann. Appl. Biol., 2:195-208. 6 pl. Lerpy, J. 1882. On Enchytraeus, Distichopus, and their Parasites. Proc. Acad. Nat. Sci. Phil., pp. 145-148. MICHAELSEN, W. 1888. Beitrige zur Kenntniss der deutschen Enchytraeiden-Fauna. Arch. f. mikr. Anat., 31:483-498. 1 pl. 1900. Oligochaeta. Das Tierreich, 10 Lief. XXXIX-++575 pp. 13 fig. Berlin. 1901. Oligochaeten der Zoologischen Museen zu St. Petersburg und Kiew. Bull. L’Acad. Imp. Sci. St. Petersbourg, (5), 15:137-215. 1903. Die geographische Verbreitung der Oligochaeten. 186 pp. 11 pl. Berlin. 1905. Die Oligochaeten des Baikal-Sees. Wissenschaftliche Ergebnisse einer Zoologischen Expedition nach dem Baikal-See unter Leitung des Professors Alexis Korotneff in den Jahren 1900-1902. Erste Lief. 68 pp. 9 fig. 1908. Die Oligochaeten der Deutschen Siidpolar-expedition 1901-1903. Deutsche Siidpolar-expedition 1901-1903, 9:1-58. 1 pl. 1911. Litorale Oligochiten von der Nordkiiste Russlands. Travaux de la Soc. Imp. Nat. St. Petersbourg, 42: 1-6. 2 fig. 1914. Beitrige zur Kenntnis der Land- und _ Siisswasserfauna Deutsch- Siidwestafrikas. Ergeb. Hamb. deutsch-siidwestafrikanischen Stu- dienreise 1911. Oligocheta, pp. 139-182. 1 pl. 1915. Ein eigentiimlicher neuer Enchytriide der Gattung Propappus aus der Niederelbe. Verh. nat. Ver. Hamburg, (3), 23:51—-53. Mookrg, J. P. 1895. The Characters of the Enchytraeid Genus Distichopus. Am. Nat., 29 :754-756. 1905. Some Marine Oligochaeta of New England. Proc. Acad. Nat. Sci. Phil., pp. 373-399. 2 pl. Situ, S. I. and Verritt, A. E. 1871. Notice of the Invertebrata dredged in Lake Superior in 1871, by the U. S. Lake Survey, under the direction of Gen. C. B. Comstock, S. I. Smith, naturalist. Am. Journ. Sci. Arts, (3), 2:448-454. SOUTHERN, R. 1907. Oligocheta of Lambay. Irish Nat., 16:68-82. 2 pl. 1909. Contributions towards a Monograph of the British and Irish Oligocheta. Proc. R. Irish Acad., 27:119-182. 5 pl. 50 PAUL S. WELCH 1913. Oligochaeta. Clare Island Survey, part 48. Proc. R. Irish Acad., Vol. 31,14 pp.1ipl. 1 fig. STEPHENSON, J. 1911. On some Littoral Oligocheta of the Clyde. Trans. R. Soc. Edinburgh, 48:31-65. ipl. 14 fig. 1915. On some Indian Oligochaeta mainly from Southern India and Ceylon. Mem. Ind. Mus., 6:35-108. 4 pl. 2 fig. VEJDOVSEY, F. 1879. Beitrige sur Vergleichenden Morphologie der Anneliden. I. Mono- graphie der Enchytraeiden. 14 pl. Prag. 1905. Ueber die Nephridien von Aeolosoma und Mesenchytraeus. Sitz. Gesell. Wiss., Math.-Naturw. Classe, pp. 1-11. 1 pl. WE cH, P. S. 1914. Studies on the Enchytreide of North America. Bull. Ill. State Lab. Nat. Hist., 10:123-212. 5 pl. 1917. Enchytreide (Oligocheta) from the Rocky Mountain Region. Trans. Am. Micr. Soc., 36:67-81. wh ~ as ute OS Se Ak . ae PLATE III TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XXXIX See geriliag ata) ER | 7 OE ul SES VON apr E jae is! A ae he Ae $2 'y de eat = te pV ao ne fos M8 Pos yp \ yi Ay Pod A af by eee) = PE ACH SE Eee aA Oscillatoriaceae HOST ALOnIAMOLMOSA yes ws eiclne cies lols) sh ellisyels) seals ciate e > Sa ALT Sia etcin trie MsaMlatonialimosa sec. e + sceiersk sed eic ss oA AUllohart ree ea tO a a PATTIMICIMNLENIU Cases iettcs ale cies) [ee anne wgiclee 2 Nira WEI eae te PHormidium valderianum’. 2). 2. es 6c. sl suse ee ws wae Bist) FINS can Maca meee Nostocaceae mabaena fOs-aquae.<. 2)... csc ease x RMN cam en a aaceaon Pana tenarOscillanoidesis vise dalss 5 cine waliecalleanlonies ey eee XE HAN (tater Acie ab ee © Pima eM Ay COTUlOSA. sess era e alas « c/a)s, cai x x x SMMLOsperna win COMALCM, .!)\0).5 5 fcc of vite vc dc tiele wallebioicie sists Be x Nodularia harveyana .............. arstedel (peach aye eptek as KI hina EN eS ce TumEMEMPBU IAG Kota oy St EN so loa boaikig Say aN tales a URE x SNe MURIEERESR GE LY TV N25 15000272, 41 218 15/2 ke Xl cbse niflal pits #i a's eel > LUN Aone eee A Pree MUSCOTUIM 2... ws oe cio vines ss x D-ce ee Mt reas kas ah une Mgstoc'spongiaeforme.................. KEN Pel arogeigaph ticle Fanart pecais tae ene eee ait Scytonemaceae Seemerema Crispum:. 2.2.6 eck sce es x x x Rivulariaceae (LT TEES a CN ST AR Ue aM aad en VC x Bacillariaceae* Cystopleura zebra Achnanthes lanceolata Eunotia diodon Cyclotella meneghiniana Eunotia lunaris Cymbella amphicephala Eunotia major Cymbella cuspidata Fragilaria construens Cymbella naviculiformis Gomphonema acuminatum Cymbella subaequalis Gomphonema constrictum Cystopleura gibba Gomphonema gracile Cystopleura gibba ventricosa Gomphonema montanum * No seasonal studies were made of diatoms. 68 Melosira varians Navicula ambigua Navicula anglica Navicula bacilliformis Navicula brebissonii Navicula cuspidata Navicula dicephala Navicula elliptica Navicula gibba brevistriata Navicula hilseana Navicula major Navicula mesolepta Navicula iridis ANDERSEN AND WALKER Navicula pupula Navicula sculpta Navicula sphaerophora Navicula stauroptera Navicula viridis Nitzschia brebissonii Stauroneis anceps Stauroneis anceps amphicephala Stauroneis phoenicenteron Surirella ovalis ovata Synedra rumpens Synedra ulna Early Mid- October summer summer Desmidiaceae Arthrodesmus convergens..............- x x x Glostertumcynthias sn. sia: iets tases apiece x x x Closterium didymotocum............... XK’ © Wades saci ee @lostertumijennenlame.s seer ieee i HCl et.0) Soe oS | eee Glosteniumrlanceolatuimep say. eee selene clsteieiis Chie cieeel|leeieisoe eee x Clostenumblunulatee ere ceric x x. x Closterium! monilifemim=..- =. oe a x x x Glostentum parvulam acs 26512. felts eatets lio oratorereisin seni x x Glosteritum pritchardianum cis) .5 cis aie leel||- stcteipiein sod sts [ses aes vs ote ee x Glostersumpsiliqua sss semis ee raciie ce lsketesl| Ootsaes erciamieta tillorece eae eee x G@losteriumistnolatumijen- eerie eet ae Kx )o..... 005082 eee Clostertumiturciduntessereie ace ey ZX Vole aces) eee Cosmariumabrptumeree rate seer ioe (teria ein it ae > REE FSS B80 0.c.c Cosmaniumbangulostmbe amare aia ede| [eves creaeterses. til operas epee x Cosmarium angulosum concinnum.......|............ x x Cosmarium | boeckineesr cere ees sete Xo) eee eee x Cosmariumibly bite anes bacon eet a|'civaens oats x x Cosmarium botrytis tumidum........... > nn EE erE mcs |ocaccsocéolr Gosmanium'circularesaseere eee e een Sh) AR x Gosmanumiconnatomipe nent ery ceric eer x x x Cosmanumicrenatum=ery eee ce > EE PAPA apa lob crate bclibc¢ Cosmarniumicychicuimiay rer cri ctr ee ie ene XW 0 wks oe eee Cosmarium cymatopleurum............. > EE PREM) la,ccc 66 Oot 3+ Cosmarium formosulum nathrostii.......]............ x x (Cosmaniumipalenttumepey eee ee eee o| cosine eee eee x; Verse eyepee Cosmanumigranarumprmmen ees etic ee cic ares x x AN ECOLOGICAL STUDY OF ALGAE 69 Early Mid- October summer summer Cosmarium*holmiensez). 25.4). 5 ccs seenle as x AG Heer x Cosmarium)jkellmani grandeé< e240: nieces oe eres es x Seep é i COSMALUMIIMENEL MUI leet eisi te sae dale <0 sillapare sin ci aoslene p clair aaa CNN Es Cosmarium microsphinctum............. 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SY SANs x » AWE ele eeeee NP : Cosmarium subtumidum...... Nonsesins al recon atid bests ba 2 Kalender oeue Cosmarium subundulatum.............. KHIM ai eens vee emer sitions aye anus ae Cosmarium taxichondrum...............].. ay Maa DN Mm a HES ete ee Cosmarium tetraophthalmum........ Sal a Sey eee és Keg yl) es eee cca fete Cosmarium trilobulatum................].. eben hepa elats x Beth as Soaionas PUREE TUMETEN SE UATE HE Flos a Aira laine afte te kee seatac x Er eistoniotals Cosmarium vexatum....... vats : NERVE POS Sry dl targetsoeer é Euastrum attenuatum.............. Siete veil avetanetecese He.cluinl isomerate x Semeersisri Dicken tatu: 1/542 6 4. hye els reine eile wincceds c retail >.< VES Caste bs oye ls oS CETE SST RTT a OTE a ae feet li x x Bwastrum dubium... 2.0.6... 4 <0: SAU Wo seven se x Sood ‘ Euastrum oblongum........ SIGE Roi tel | Tae Rea , x x Euastrum verrucosum........ Ne eee et: x x x Huastrum! verrucosum alatum. ...02.0%. 04 o AMER: CORR PENI ESI Wrecks 5 Spirogyra Gublaaee cesta. Rive siecle x x x Spiropyra lutetianar .2- cisco en <0) -eieivelsie Kh atthe st. oe ee rr Splrageyaa Mer lecka mam cere piss steve iste alia Ste folaioxel eet i2ie (ate ol lovee lore ere halal x Spirogyra WAniamS a yom re oe iostseyae siete axe | ele seye layers): os fal eheie te eiela ame jorels x LY ENEMAS ace eee eters afore elelet oka: x x x Mesocar paceae Mougeotiarobuscaere rn carr ici c Gist ielll-ireys este, cie erie | slave e eee amet x IMonpzeotia Sealarise ret nies ct leiayale sida iaeeiels ic avi viaiisl| s/.e oy aE x Mougeotia viridiste.o4--ris fee seco > EE REARS alles ooo. coc Volvocaceae Volvox(aureuste mae see itocncioi eee ice |siaesiSeniens ct p a RIE ime Tetras poraceae Dictyosphaerium pulchellum............].........00. x x Tetraspora Pelatinosa ye. c ses o ices sire = > ne Ere AN a aotMino koto o¢ AN ECOLOGICAL STUDY OF ALGAE pint Early summer Pleurococcaceae Mid- October summer Crucigeniamrectangularish ss sste tots sre ache teh cletate Rotini Gee Un Seeds x PEMEMOSPUACTS VIFIGIS s siais/oiG (0,6 Sie ceheey oi erence ffele mveid ladle one ate Nephrocytiummaegeliiyete ee lye oe see erate x OGYSHSISOWMPa RIA ha tects chee evel elaraisisr ede Silt aeevers ature ees Rhaphidium polymorphum falcatum.....|............ Scenedesmus antennatus............... Scenedesmus bijugatus................. ee sO ? PPEErACORONETe LIC MAGLI Mee crepes seal ceat ale | aU spai cient anual abereia eis eee x RU OGOECUSHIITSIOTIS Mean U Nis ae. yey e k toctiorclli aly USUI MOIA SMR RO PRN ULEE CN IR x Protococcaceae Gloeocystis vesciculosa................- x Ps@cy Aa CAPYER TUT Veale Na AO IMMUN A) x Hydrodictyaceae BHSIALHOMISPNACHICUNA: (eis s/c) \ 5 waders Coarse) ates Malaoals cans Pediastrumiang ulosmany yer narsra aia ans Mh ae | MINUS MCN) ee alia Cie | x Pegiastriusy DOryanUHN |). 20.2 a), ie ake S x IBEGIASEMIMLLELEAS Sainte MEL Nein hokey aca MAIN Ujanaaiah Ulotrichaceae iiterosporaypachy derma! cei Milk aw eC As IMIGrOSpOTA SLAM ORM oho) e)dsrcitie se clase dais hess enol nis Chaetophoraceae Stigeoclonium glomeratum.............. x Oedogoniaceae | SUL OCS Sut o aed Aiea Uo ey Ache diate RU A a] WAS Aa x Gedagoniam: spi:'4 +4 sageteisetak awe oes x Oedogonium capilliforme australe........}............ Oedogonium cardiacum.. 2 .j)..0460.) 005). x Oedogonium crispum uruguayense........ x GCraoronnim: fragile yoy acy ec ntars eat uate eh eat es economy Varian’). 0 igh ras hy aba sia oUt el Mia tis Cena x Cladophoraceae Rhizoclonium hieroglyphicum........... x oija| eiejislelle|.eveol/al se} syeltm («reise .eueteleia de ANDERSEN AND WALKER V aucheriaceae Early Mid- October summer summer Vaueheria Spices cian a oe hots cre ree © eet ete leliicte a ne arate e aera tate a x BIG ALKALI LAKE Big Alkali Lake (Fig. 1) is a little larger than Clear lake. While it is more alkaline than Hackberry, Dewey, or Watts, it is far less so than Clear lake. The water had the characteristic yellow color of the alkaline lakes of this region. Here again alkalinity must be given as the factor governing the algal flora of the lake. One visit only was made here. At first sight the water seemed absolutely barren but further investigation showed the following forms to be present. The Chara was quite abundant forming very much dwarfed patches on the bottom near the shore. Chroococcaceae Clathrocystis aeruginosa Merismopedium glaucum Merismopedium tenuissimum Oscillatoriaceae Oscillatoria limosa Bacillariaceae Amphora ovalis Campylodiscus clypeus Cymbella cistula Cystopleura gibba Navicula cryptocephala veneta Navicula gastrum Navicula oblonga Navicula sculpta Desmidiaceae Cosmarium angulosum Cosmarium granatum Cosmarium meneghinii Cosmarium sexnotatum Staurastrum gracile Staurastrum paradoxum Staurastrum polymorphum Tetras poraceae Dictyosphaerium pulchellum Pleurococcaceae Scenedesmus bijugatus Scenedesmus obliquus Scenedesmus quadricauda Hydrodictyaceae Pediastrum boryanum Pediastrum duplex clathratum Characeae Chara foetida rabenhorstii DEWEY LAKE Dewey lake (Fig. 1) is situated about half a mile from Hack- berry lake. It is less alkaline, nearly three times as large and propor- tionally deeper. Otherwise the conditions were much the same. Temperatures taken in the region of algal growth showed little varia- tion from those in Hackberry lake. AN ECOLOGICAL STUDY OF ALGAE 73 The algae were found along the margins of the lake and attached to submerged plants near the surface. As no attempt was made to study conditions in this lake no explanation of the conspicuous differ- ence in the forms found can be given unless it was the larger amount of water and difference in alkalinity. Collections were made here at irregular intervals and the list must not be looked upon as complete. Chroococcaceae Clathrocystis aeruginosa Merismopedium glaucum Oscillatoriaceae Beggiatoa alba Lyngbya aerugineo-caerulea Oscillatoria amphibia Oscillatoria formosa Oscillatoria subtilissima Phormidium fragile Phormidium tenue Phormidium valderianum Nostocaceae Anabaena flos-aquae Nostoc linckia Nostoc pruniforme Scytonemaceae Tolypothrix distorta Rivulariaceae Rivularia echinulata Rivularia natans Bacillariaceae Amorpha ovalis Brebissonia vulgaris Cocconeis placentula Cymbella cistula Cymbella cuspidata Cymbella lanceolata Encyonema turgidum Eunotia lunaris Fragilaria capucina Fragilaria construens binodis Gomphonema constrictum Gomphonema gracile Gomphonema montanum Gomphonema parvulum Navicula cuspidata Navicula lanceolata Navicula major Navicula oblonga Navicula pupula Staureneis acuta Stauroneis smithii Stauroneis tenuissima Synedra rumpens Synedra ulna Desmidiaceae Closterium pritchardianum Cosmarium blyttii Cosmarium boeckii Cosmarium formosulum nathorstii Cosmarium impressulum Cosmarium obtusatum Cosmarium ochthodes var. Cosmarium subcrenatum Cosmarium turpinii podolicum Cosmarium vexatum Penium margaritaceum Staurastrum orbiculare Pleurococcaceae Scenedesmus bijugatus Scenedesmus obliquus Tetraedron trigonum Protococcaceae Characium ambiguum Characium subulatum Gloeocystis vesciculosa Hydrodictyaceae Pediastrum boryanum Ulotrichaceae Hormiscia subtilis variabilis Chaetophoraceae Chaetophora elegans Gongrosira debaryana Stigeoclonium aestivale 74 ANDERSEN AND WALKER Stigeoclonium glomeratum Oedogontaceae Oedogonium grande Oedogonium vaucherii Helminthocladiaceae Batrachospermum vagum WATTS LAKE Watts lake (Fig. 1) is about half the size of Hackberry and only about one-third of a mile from it. Conditions in the lake were very similar to those in Hackberry in every respect. It was, however, slightly less alkaline than Dewey lake. Collections were made here about once a week but other data were not taken. No boat was available on this lake and that may account for some of the difference in the reports for Watts and Hackberry lakes. No reason for a difference in species could be given unless it were the slight difference in alkalinity. The following species were found which it will be noted are nearly all included in those found in Hackberry and Dewey lakes and the springs on the shore of Clear lake. Cosmarium geminatum Cosmarium granatum Cosmarium obtusatum Cosmarium phaseolus Cosmarium pseudopyramidatum Cosmarium subcrenatum Staurastrum gracile Staurastrum margaritaceum Chroococcaceae Clathrocystis aeruginosa Coelosphaerium kuetzingianum Merismopedium tenuissimum Microcystis marginata Nostocaceae Nostoc pruniforme Bacillariaceae Tetras poraceae Achnanthes lanceolata Dictyosphaerium pulchellum Amphora ovalis Pleurococcaceae Cocconeis placentula Gomphonema gracile Gomphonema montanum Homoeocladia amphioxys Navicula gastrum Oocystis solitaria Scenedesmus bijugatus Scenedesmus obliquus Scenedesmus quadricauda Tetraedron minimum Navicula lanceolata Hydrodictyaceae Desmidiaceae Pediastrum boryanum Cosmarium boeckii Characeae Cosmarium formosulum nathorstii Chara contraria OTHER LAKES One visit was made to each of the following lakes in the early summer. Trout and Dad’s lakes (Fig. 1) are among the larger of the AN ECOLOGICAL STUDY OF ALGAE 75 group while Phalaris (Fig. 1) is one of the smaller. The Snake Creek Falls, about 15 miles distant, were visited once. These are falls in a creek which flows through the sandhill region. These collections were made so superficially that the lists must stand only as representing some species found in these localities. The only form found which was sufficiently conspicuous to need special mention was Nostoc verrucosum which was extremely abundant on rocks in the cataract below the falls in Snake Creek. The forms found in these localities are as follows: PHALARIS LAKE Chroococcaceae Coelosphaerium kuetzingianum Merismopedium tenuissimum Dactylococcopsis rhaphidioides Bacillariaceae Amphora ovalis Cocconeis placentula Cystopleura gibba Cystopleura turgida Gomphonema montanum Homoeocladia amphibia Navicula cryptocephala veneta Navicula cuspidata Navicula elliptica Navicula gastrum Navicula oblonga Navicula sculpta Navicula sphaerophora Sceptroneis fibula Chroococcaceae Clathrocystis aeruginosa Nostocaceae Anabaena flos-aquae Nostoc zetterstedtii Chroococcaceae Clathrocystis aeruginosa Desmidiaceae Closterium acerosum Desmidiaceae Cosmarium angulosum Cosmarium blyttii Cosmarium formosulum nathorstii Cosmarium granatum subgranatum Cosmarium obtusatum Cosmarium regnellii Tetras poraceae Dictyosphaerium pulchellum Pleurococcaceae Oocystis solitaria Pediastrum boryanum Scenedesmus bijugatus Scenedesmus quadricauda Tetraedron minimum Characeae Chara contraria Chara evoluta Chara fragilis TROUT LAKE DAD’S LAKE Chara sp. Hydrodictyaceae Pediastrum angulosum Characeae Chara sp. Tetras poraceae Dictyosphaerium pulchellum Hydrodictyaceae Pediastrum boryanum Pediastrum duplex clathratum 76 ANDERSEN AND WALKER Chroococcaceae Merismopedium glaucum Oscillatoriaceae Arthrospira jenneri Oscillatoria brevis Oscillatoria formosa Phormidium retzii Nostocaceae Nostoe pruniforme Nostoc verrucosum Rivulariaceae Calothrix parietina Bacillariaceae Achnanthes lanceolata Amphora ovalis Cocconeis placentula Cymbella amphicephala Cymbella cuspidata Cymbella ehrenbergii Cymbella gastroides Cystopleura gibba Cystopleura ocellata Cystopleura turgida Cystopleura zebra Denticula elegans Encyonema turgidum Eunotia major Fragilaria mutabilis Gomphonema acuminatum Gomphonema herculeanum Lysigonium crenulatum Lysigonium distans Navicula ambigua Navicula anglica Navicula appendiculata Navicula brebissonii Navicula cuspidata craticula Navicula dicephala Navicula elliptica SNAKE FALLS Navicula humilis Navicula iridis Navicula lanceolata Navicula limosa Navicula gibba brevistriata Navicula mesolepta Navicula pupula Navicula radiosa Navicula sculpta Navicula viridis Homoeocladia amphibia Homoeocladia brebissonii Homoeocladia amphioxys Homoeocladia palea Rhoicosphenia curvata Sceptroneis pacifica Stauroneis anceps Stauroneis phoenicenteron Surirella robusta Surirella spiralis Synedra ulna Tetracyclus lacustris Desmidiaceae Closterium striolatum Cosmarium microsphinctum Cosmarium portianum Cosmarium sportella Cosmarium undulatum wollei Euastrum oblongum Euastrum verrucosum Penium margaritaceum Staurastrum orbiculare hibernicum Pleurococcaceae Scenedesmus obliquus Protococcaceae Chlorococcum humicola Cladophoraceae Cladophora glomerata CONCLUSION It appears even from so brief a study as the one just described that the occurrence of algae in a given body of water at a given time is AN ECOLOGICAL STUDY OF ALGAE ih due, to a certain extent, as Transeau (44), West (49), and others have said, to seasonal periodicity. It is also evident that West (48 and 50), Oltmanns (34), Brannon (12), Wipple and Parker (53), Chambers (15), and many others are correct in their decisions that the mineral and gas content of water has much to do with its algal flora. Of these factors, alkalinity is probably to a great extent, the explanation for the wide difference in the algal flora of lakes so close together and so uniform in all other factors. In a given lake the distribution of species may be explained by the one factor only that is variable, namely light intensity. Means for measuring this factor were entirely inefficient and only the crudest estimates can be made. In small bodies of water where even the light is not variable to any measurable degree the dominant species and its associates are determined merely by chance except that forms lying beneath other forms are more shaded. This exception does not affect the dominant species but may affect the forms associated with it. ALGAE FOUND IN CHERRY COUNTY Chroccoccaceae. Oscillatoria limosa. (Roth) Ag. Aphanothece prasina A. Braun Clathrocystis aeruginosa (Kuetz.) Henfrey Coelosphaerium kuetzingianum Naeg. Dactylococcopsis rhaphidioides Hansg. Gloeocapsa arenaria (Hassall) Rabenh. Merismopedium aerugineum Bréb. Merismopedium glaucum (Ehrb.) Naeg. Merismopedium tenuissimum Lem- merm. Microcystis marginata (Menegh.) Kuetz. Oscillatoriaceae. Arthrospira jenneri (Kuetz.) Stiz. Lyngbya aerugineo-caerulea (Kuetz.) Gom. Oscillatoria amphibia Ag. Oscillatoria brevis (Kuetz.) Gom. Oscillatoria formosa Bory. Oscillatoria princeps Vauch. Oscillatoria sancta (Kuetz.) Gom. Oscillatoria subtilissima Kuetz. Oscillatoria tenuis Ag. Phormidium fragile (Menegh.) Gom. Phormidium retzii (Ag.) Gom. Phormidium tenue (Menegh.) Gom. Phormidium valderianum (Delp.) Gom. Spirulina major Kuetz. Nostocaceae. Anabaena flos-aquae (Lyngb.) Bréb. Anabaena oscillarioides Bory. Anabaena torulosa (Carmich.) Lager- heim Cylindrospermum comatum Wood Cylindrospermum majus Kuetz. Nodularia harveyana(Thwaites) Thuret Nostoc austini Wood Nostoc caeruleum Lyngbye 78 Nostoc commune Vaucher Nostoc glomeratum Kuetz. Nostoc humifusum Carmichael Nostoc linckia (Roth) Bornet Nostoc minutum Desm. Nostoc muscorum Ag. Nostoc pruniforme (L.) Ag. Nostoc spongiaeforme Ag. Nostoc verrucosum (L.) Vauch. Nostoc zetterstedtii Areschoug Scy tonemaceae. Scytonema crispum (Ag.) Bornet Tolypothrix distorta (Hofm. B.) Kuetz. Rivulariaceae. Calothrix parietina (Naeg.) Thur. Rivularia echinulata (Smith) Born Rivularia natans (Hedw.) Welw. Rivularia pisum Ag. Bacillariaceae. Achnanthes lanceolata (Bréb.) Gr. Amorpha ovalis (Bréb.) Kuetz. Brebissonia vulgaris (Thwait) Kunze Campylodiscus clypeus Ehr. Cocconeis placentula Ehr. Cyclotella meneghiniana Kuetz. Cymbella amphicephala Naeg. Cymbella cistula (Hempr.) Kirchn. Cymbella cuspidata Kuetz. Cymbella cymbiformis (Kuetz.) Bréb. Cymbella ehrenbergii Kuetz. Cymbella lanceolata (Ehr.) Kirch. Cymbella naviculiformis Auersw. Cymbella subaequalis Grun. Cystopleura gibba (Ehr.) Kunze Cystopleura zebra (Ehr.) Kunze Encyonema turgidum (Greg.) Grun. Eunotia diodon Ehr. Eunotia lunaris Grun. Eunotia major (W. Sm.) Rabenh. Fragilaria capucina Desmaz. Fragilaria construens (Ehr.) Grun. Fragilaria construens binodis (Ehr.) Grun. Gomphonema acuminatum Ehr. Gomphonema constrictum Ehr. ANDERSEN AND WALKER Gomphonema gracile Ehr. Gomphonema herculeanum Ehr. Gomphonema montanum Schum. Gomphonema parvulum Kuetz. Homoeocladia amphibia (Grun.) Kunze Homoeocladia amphioxys (Ehr.) Kunze Homoecladia brebissonii (H. Sm.) Kunze Homoeocladia palea (Kuetz.) Kunze Lysigonium crenulatum (Kuetz.) Kunze Lysigonium distans (Kuetz.) Kunze Lysigonium varians (Ag.) D.T. Navicula ambigua Ehr. Navicula anglica Ralfs Navicula appendiculata (Ag.) Kuetz. Navicula bacilliformis Grun. Navicula brebissonii Kuetz. Navicula cryptocephala veneta (Kuetz.) Rhabenh, Navicula cuspidata Kuetz. Navicula dicephala Ehr. Navicula elliptica Kuetz. Navicula gastrum Ehr. Navicula gibba (Ehr.) Kuetz. Navicula gibba brevistriata Grim. Navicula hilseana Jan. Navicula humilis Donk. Navicula iridis Ehr. Navicula lanceolata Kuetz. Navicula limosa Kuetz. Navicula major Kuetz. Navicula mesolepta Ehr. Navicula oblonga Kuetz. Navicula pupula Kuetz. Navicula radiosa Kuetz. Navicula sculpta Ehr. Navicula sphaerophora Kuetz. Navicula stauroptera Grun. Navicula subcapitata Greg. Navicula viridis Kuetz. Nitzschia brebissonii W. Sm. Nitzschia spectabilis (Ehr.) Ralfs Nitzschia tryblionella Hantzsch. Rhoicosphenia curvata Grun. Sceptroneis fibula (Bréb.) Schuett AN ECOLOGICAL STUDY OF ALGAE 79 Sceptroneis pacifica (Grun.) Elmore (In press) Stauroneis anceps Ehr. Stauroneis anceps amphicephala Kuetz. Stauroneis acuta W. Sm. Stauroneis phoenicenteron Ehr. Stauroneis smithii Grun. Surirella ovalis ovata (Bréb.) V.H. Surirella ovalis pinnata (Bréb.) V.H. Surirella robusta Ehr. Surirella spiralis Kuetz. Synedra rumpens Kuetz. Synedra ulna (Nitzsch.) Ehr. Tetracyclus lacustris Ralfs Desmidiaceae. Arthrodesmus convergens Ehrenb. Closterium acerosum (Schrank) Ehrenb. Closterium aciculare Tuffen West Closterium cynthia DeNot. Closterium didymotocum Corda Closterium jenneri Ralfs Closterium lanceolatum Kuetz. Closterium leibleinii Kuetz. Closterium lunula (Muell.) Nitzsch. Closterium moniliferum (Bory). Ehrenb. Closterium parvulum Naeg. Closterium pritchardianum Arch. Closterium siliqua West and G. S. West Closterium striolatum Ehrenb. Closterium turgidum Ehrenb. Cosmarium abruptum Lund. Cosmarium angulosum Bréb. Cosmarium angulosum concinnum (Rabenh.) West and G. S. West Cosmarium blyttii Wille Cosmarium boeckii Wille Cosmarium botrytis tumidum Wolle Cosmarium circulare Reinsch. Cosmarium connatum Bréb. Cosmarium crenatum Ralfs Cosmarium cyclicum Lund. Cosmarium cymatopleurum Nordst, Cosmarium elfingii Racib. Cosmarium formosulum nathorstii (Boldt) West and G. S. West Cosmarium galeritum Nordst. Cosmarium geminatum Lund. Cosmarium granatum Bréb. Cosmarium granatum subgranatum Nordst. Cosmarium holmiense Lund. Cosmarium holmiense integrum Lund. Cosmarium impressulum Elfv. Cosmarium kjellmani grande Wille Cosmarium laeve Rabenh. Cosmarium meneghinii Bréb. Cosmarium microsphinctum Nordst. Cosmarium notabile Bréb. Cosmarium obtusatum Schmidle Cosmarium ochthodes Nordst. var. Cosmarium pachydermum Lund. Cosmarium pachydermum aethiopi- cum West and G. S. West Cosmarium phaseolus Bréb. Cosmarium phaseolus elevatum Nordst. Cosmarium phaseolus minor Boldt Cosmarium portianum Arch. Cosmarium protractum (Naeg.) De- Bary Cosmarium pseudopyramidatum Lund. Cosmarium pygmaeum Arch. Cosmarium pyramidatum Bréb. Cosmarium rectangulare hexagonum (Elf.) West and G. S. West Cosmarium regnellii Wille Cosmarium retusiforme (Wille) Gutw. Cosmarium sexnotatum Gutw. Cosmarium sportella Bréb. Cosmarium subcrenatum Hantzsch Cosmarium subtumidum Nordst. Cosmarium subundulatum Wille Cosmarium taxichondrum Lund. Cosmarium tetraophthalmum Bréb. Cosmarium trilobulatum Reinsch Cosmarium tumidum Lund. Cosmarium turpinii podolicum Gutw. Cosmarium umbilicatum Luetkem. 80 Cosmarium undulatum wollei West Cosmarium vexatum West Euastrum attenuatum Wolle Euastrum bidentatum Naeg. Euastrum binale (Turp.) Ehrenb. Euastrum dubium Naeg. Euastrum oblongum (Grev.) Ralfs Euastrum verrucosum Ehrenb. Euastrum verrucosum alatum Wolle Micrasterias pinnatifida (Kuetz.) Ralfs Micrasterias rotata (Grev.) Ralfs Netrium digitus (Ehrenb.) Itzigs and Rothe Netrium interruptum (Bréb.) Luetkem. Pleurotaenium coronatum (Bréb.) Rabenh. Penium libellula (Focke) Nordst. Penium margaritaceum (Ehrenb.) Bréb. Penium naegelii Bréb. Penium spirostriolatum Barker Pleurotaenium nodulosum (Bréb.) De- Bary Pleurotaenium trabecula (Ehrenb.) Naeg. Spirotaenia condensata Bréb. Spirotaenia obscura Ralfs Spirotaenia trabeculata A. Br. Staurastrum alternans Bréb. Staurastrum dickiei Ralfs Staurastrum dilatatum Ehrenb. Staurastrum dispar Bréb. Staurastrum gracile Ralfs Staurastrum hirsutum (Ehrenb.) Bréb. Staurastrum margaritaceum Ehrenb. Staurastrum meriani Reinsch Staurastrum muticum Bréb. Staurastrum orbiculare (Ehrenb.) Ralfs Staurastrum orbiculare hibernicum West and G. S. West Staurastrum orbiculare ralfsii West and G. S. West Staurastrum paradoxum Meyen Staurastrum paxilliferum G. S. West Staurastrum polymorphum Bréb. ANDERSEN AND WALKER Staurastrum punctulatum Bréb. Staurastrum saxonicum Bulnh. Staurastrum teliferum Ralfs Zygnemaceae. Spirogyra arcta catenaeformis Kirchn. Spirogyra crassa Kuetz. Spirogyra dubia Kuetz. Spirogyra lutetiana Petit Spirogyra neglecta (Hass.) Kuetz. Spirogyra varians (Hass.) Kuetz. Zygnema Ag. sp. Mesocarpaceae. Mougeotia robusta (DeBary) Wittr. Mougeotia scalaris Hass. Mougeotia viridis (Kuetz.) Wittr. Volvocaceae. Volvox aureus Ehrenb. Tetrasporaceae. Tetraspora gelatinosa (Vauch.) Desv. Dictyosphaerium pulchellum Wood Pleurococcaceae. Crucigenia rectangularis (A. Br.) Gay Eremosphaera viridis DeBary Nephrocytium naegelii Grun. Oocystis solitaria Wittr. Rhaphidium polymorphum falcatum (Corda) Rabenh. Scenedesmus antennatus Bréb. Scenedesmus bijugatus (Turp.) Kuetz. Scenedesmus obliquus (Turp.) Kuetz. Scenedesmus quadricauda (Turp.) Bréb. Tetraedron minimum Reinsch Tetraedron reticulatum (Reinsch) Hansg. Tetraedron trigonum (Naeg.) Hansg. Urococcus insignis Hass. Protococcaceae. Characium ambiguum Hermann Chlorococcum humicola (Naeg.) Rabenh. Characium subulatum A. Br. Gloeocystis gigas (Kuetz.) Lagerh. Gloeocystis vesciculosa Naeg. Ophiocytium capitatum Wolle AN ECOLOGICAL STUDY OF ALGAE 81 Hydrodictyaceae. Coelastrum sphaericum Naeg. Pediastzum angulosum (Ehrenb.) Menegh. Pediastrum boryanum Menegh. Pediastrum duplex clathratum A. Br. Pediastrum tetras (Ehrenb.) Ralfs (Turp.) Ulotrichaceae Microspora amoena (Kuetz.) Rabenh. Microspora pachyderma (Wille) Lagerh. Microspora stagnorum (Kuetz.) Lagerh. Hormiscia subtilis variabilis (Kuetz.) Kirchn. Chaetophoraceae. Chaetophora cornu-damae (Roth) Ag. Chaetophora elegans (Roth) Ag. Gongrosira debaryana Rabenhorst Stigeoclonium aestivale (Hazen) Col- lins Stigeoclonium glomeratum (Hazen) Collins Oedogoniaceae. Bulbochaete Ag. sp. Oedogonium Link (several species not in fruit.) Oedogonium capilliforme australe Wittr. Oedogonium cardiacum (Hass.) Kuetz. Oedogonium crispum uruguayense Magn. and Wille Oedogonium fragile Wittr. Oedogonium grande Kuetz. Oedogonium varians Wittr. and Lund. Oedogonium vaucherii (LeCl.) A. Br. Coleochaetaceae. Coleochaete orbicularis Pringsh. Cladophoraceae. Cladophora glomerata (L.) Kuetz. Rhizoclonium hieroglyphicum (Ag.) Kuetz. Vaucheriaceae. Vaucheria D.C. sp. Characeae. Chara Vaill. sp. Chara contraria A. Br. Chara evoluta Allen Chara foetida rabenhorstii T. F. Allen Chara fragilis Desv. Helminthocladiaceae. Batrachospermum vagum Ag. PUBLICATIONS CONSULTED 1. Agardh, J. G. Species, genera, et ordines algarum. 3 vols. 1848-1880. 2. Allen, T. F. Characeae Americanae, illustrated and described. Parts I and II. 1879. 3. ——————. The Characeae of America, PartsI and II. 1880. 4, ———_———. Characeae. N. Y. State Museum Nat. Hist. 38th ann. report. 16, 15 Jan. 1885. 5. ——————.. The Characeae of America. Parts I and II, Fasc. 1, 2, and 3. 1888-1896. 6. Bessey, Charles E. Supplementary list of recently reported species. Webber’s appendix to the catalogue of the flora of Nebraska, second edition. tions from the Bot. Dept. of the Uni. of Nebr. Contribu- New series III:45-53, 1892. 7. Bessey, Charles E. and Webber, H. J. Report of the botanist on the grasses and forage plants and the catalogue of plants. Nebraska State Board of Agriculture. Extracted from the report of the 1889-1890. 8. Botanical Survey of Nebraska, conducted by the Botanical Seminar, II, 1892, and EIT, 1893; 82 16. leis 18. 19. 20. ae 22: 23% 24. 25. 26. 27. 28. 29. 30. 31. Rye Sep ANDERSEN AND WALKER . Survey of Nebraska, conducted by the Botanical Seminar IV. Report on collec- tions made in 1894-1895. 1896. —————. Report on recent collections, Bot. Survey of Nebraska, pub. by Bot. Sem. 1901. . Birge, E. A. Absorption of the sun’s energy by lakes. Science, 38:702. 1913. . Brannon, M. A. Factors influencing the flora of Devil’s Lake, North Dakota. Int. Rev. d. ges. Hydr. u. Hydro. 4:291. 1911. . Brown, H. E. Algal periodicity in ponds and streams. Bull. Tor. Bot. Club, 35:223-248. 1908. . Brown, Wm. H. The plant life of Ellis, Great, Little, and Long’s Lakes in North Carolina. Contr. from the U. S. Nat. Herb. 13:323-341. 1911. . Chambers, C. O. The relation of algae to dissolved oxygen and carbon-dioxide, with special reference to carbonates. 23rd ann. report Mo. Bot. Garden, pp. 171-207. 1912. Collins, F. S. Green algae of North America. Tufts College Studies, vol. II, No. 3, pp. 79-480. 18 pls. 1909. Comére, Joseph. De l’action du milieu consedérée dans ses rapports avec la distribution générale des algues d’eau douce. Mem. 25, Bull. Soc. Bot. France, 16:1-96. 1913. Cook, M. C. British Desmids. 1887. —————. British fresh-water algae exclusive of the Desmidiaceae and Dia- tomaceae. 2 vols. 1882-1884. Copeland, W. F. Periodicity in Spirogyra. Bot. Gaz. 47:9-25. 1909. Danforth, C. H. Periodicity in Spirogyra with special reference to the work of Benecke. Ann. Rep. Mo. Bot. Garden, 21:49-59. 1910. Dangeard, P. A. Determination of the rays concerned in chlorophyll synthesis. Bul. Soc. Bot. France 60:166-175. 1914. DeToni, J. Bapt. Sylloge algarum I, 1889, V, 1907, IV, 1897-1905. Engler, A. und Prantl, K. Die natiirlichen Pflanzenfamilien, Teil I. 1897-1900. Fritsch, F. E. and Rich, Florence. Studies on the occurrence and reproduction of British fresh-water algae in nature. Ann. Bot. 21:423-436. 1907. Gomont, M. Maurice. Monographie des Oscillariees. (Nostocacees Homo- cystees). 1893. Halstedt, P. D. Classification and description of the American species of Chara- ceae. Proc. Boston Soc. Nat. Hist. XX. 1879. Hassall, Arthur Hill. A history of British fresh-water algae. 1845. Hirn, K. Monographie und Iconographie der Oedogoniaceen. Acta Soc. Sci. Fennicae 27. 1900. Kiitzing, F. T. Phycologia generalis oder Anatomie, Physiologie, und System- kunde der Tange. 1843. Migula, W. Kryptogamen-Flora von Deutschland, Deutsch-Osterreich, und der Schweiz’ im Anschluss an Thome’s Flora von Deutschland. Band II: 1 Teil, 1907, und 2 Teil, 1909. Murray, Sir John and Hjort, Dr. Johan. The depths of the ocean. 1912. Needham, James G. and Lloyd, J.T. Thelife of inland waters. 1916. 43. 33. 54. SD: AN ECOLOGICAL STUDY OF ALGAE 83 . Oltmanns, Dr. Friedrich. Morphologie und Biologie der Algen. 2 vols. 1905. . Petit, Paul. Spirogyra des environs de Paris avec XII planches. 1880. . Pool, R. J. A study of the vegetation of the sandhills of Nebraska. Minnesota Botanical Studies, Vol. 4, Part III. 1914. . Rabenhorst, Ludovico. Flora europaea algarum aquae dulcis et submarinae. 1864-1868. . Robbins, W. W. A preliminary list of the algae of Colorado. Univ. of Colo. Studies, 9:105. 1912. . Robinson, Ch. Budd. The Chareae of North America. Bull. N. Y. Bot. Garden 4: 244. 1906. . Saunders, D. and Woods, A. F. Flora of Nebraska, published by the Bot. Sem. Parts land II. 1894. . Schmidle, W. Einige Algen aus Denver, Colorado, U. S. Hedwigia 34:84-85. Figs. 1, 2, 3a, and 3b. 1895. . Smith, J. G. and Pound, R. Flora of the sandhill region of Sheridan and Cherry counties and lists of plants collected on a journey through the sandhills in July and August, 1892. Bot. Sur. Nebr. II. 1893. Tilden, Josephine E. The Myxophyceae of North America and adjacent regions including Central America, Greenland, Bermuda, the West Indies, and Hawaii. Minnesota Algae TI. 1910. . Transeau, Edgar N. The periodicity of algae in Illinois. Trans. Am. Mic. Soc. erst. 1913: . Webber, H. J. Fresh-water algae of the plains. Am. Nat. 23:1011-1013. 1889. A second edition of Webber’s appendix to the catalogue of the Flora of Nebraska. Contributions from the Bot. Dept. of the Univ. of Nebr. New series III:1-44. 1892. Appendix to the catalogue of the Flora of Nebraska. Contribution from the Shaw School of Botany. No.9. Trans. Acad. of Sc. St. Louis, 6:1-47. 1892. . West, G.S. A treatise on British fresh-water algae. 1904. The algae of the Yan Yean reservoir, Victoria; a biological and ecological study. Jour. Linn. Soc. 39:1-80. 1909. Algae. Vol. I. 1916. . West, W. and West, G. S. A monograph of the British Desmidiaceae. 4 vols. 1904-1912. On the periodicity of the Phytoplankton of some British lakes. Jour. Linn. Soc. 40:395-432. 1912. Whipple, G. C. and Parker, H. N. On the amount of oxygen and carbonic acid in natural waters and the effect of these gases upon the occurrence of micro- scopic organisms. Trans. Am. Mic. Soc. 23:103-144. 1902. Wolle, Rev. Francis. Desmids of the United States and list of American Pedia- strums with 1,100 illustrations. 1884. Fresh-water algae of the United States, (exclusive of the Diatoma- ceae) complimental to desmids of the U. S., with 2,300 illustrations. 1887. 84 Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. ANDERSEN AND WALKER EXPLANATION OF FIGURES 1. Map showing the lake region in Cherry County, Nebraska. Clear white areas represent water, dotted areas wet meadows, and _|I|I II IL/I| swamps. (From map by Dr. G. E. Condra). 2. A view taken from the top of a sandhill and showing at the front left a part of Clear lake, at the upper left a part of Dewey lake and in the distance at the right a narrow strip of White Water lake, also the “sandhills’’ and the meadows sur- rounding the lakes. (Photo by F. H. Shoemaker). 3. Hackberry lake from the northeast shore. 4. Taking water photometer records among the rushes on Hackberry lake. 5. Submerged moss stems covered with Nostoc glomeratum—Hackberry lake. (Photographed under water). 6. Section of Scirpus stem covered with Chaetophora cornu-damae and Nostoc glomeratum. (Photographed under water). 7. Water photometer records on solio paper. Upper row exposures made in air. Three lower lows exposures made under water. 8. Thermographs and anemometers in a blowout near the shore of Hackberry lake. 9. Thermographs and anemometers in the grassy meadow on the shore of Hack- berry lake. 10. Lower end of water photometer showing water tight drum and window covered with ray filter. (Photo by F. H. Shoemaker.) 11. Upper end of water photometer showing lever by means of which successive areas of the photographic plate may be exposed to the window. (Photo by F. H. Shoemaker.) 12. Above, under side of upper half of drum showing perforated, revolving disk to which photographic plates are attached by means of two clips. (Photo by F. H. Shoemaker.) 12. Below, upper half of water tight drum with lower half and tube removed. (Photo by F. H. Shoemaker.) 13. Clear lake from a sandhill at its southwest end. At the right in the distance a narrow strip of Willow lake. (X) the location of springs shown in fig. 14. 14. Pockets of spring water on the southwest shore of Clear lake. 15. Chart showing: A, temperature of air; B, temperature of soil 8 inches below surface; and C, temperature of surface soil at a station in a blowout near the shore of Hackberry lake. Also D, temperature of air in shade of a building on the lake shore; E, wind velocity at the rim of the blowout; and F, wind velocity at the bottom of the same blowout. Numbers at the left indicate, above tempera- ture in Fahrenheit and below miles per hour of wind velocity. 16. Chart showing: A, temperature of air; B, temperature of soil eight inches below the surface; and C, temperature of surface soil at a station in the grass near the lake shore; also D, temperature of air in the shade of a building on the lake shore; and E, wind velocity for the same period. Numbers at left indicate, above temperature in Fahrenheit and below miles per hour of wind velocity at the station. ty TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY PLATE X June 24 June 25 | Tune 26 VOL. XXXIX June 27 June 24 Tune 30 ANDERSEN AND WALKER Gi, TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XXXIX u i uly 3 ul Tuly & Tu Tal Se cf = ‘ Hck 1 fall ! \ A 1 | \ f ‘ i! ; H! \ RE cay \ i} \ aay ., PLATE XI Fig. 16. ANDERSEN AND WALKER TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY, VOL. XXXIX Jul 4 July 10 July s/t July 72 Jul 13 Jul 74 July IS July 76 Tuli 77 Jul 15 Jul 19 Jul 20 Juli 2/7 Jul 92 dul L Jul 24 Jul ag July 26 Tul 2 aes aa IA T_T A GING ri AGRA | ARAVA act PAW ANAL LIL al AAP rth wr Evy EP oe n_ ale PSO Saat PLATE XII Fig. 17. ANDERSEN AND WALKER aS — SS ERS p LF VOL. XXXIX cals Aug 4 July 37 Auda. 7 duly 29 July 2S | July26 July 2 Juty 23 WAG PEE aUNUaUATE Neo T CO Se ace a oc al ) WALKER Aug. € AN ECOLOGICAL STUDY OF ALGAE 85 Fig. 1/. Chart showing: A, air temperature; B, temperature of water at the bottom of lake (3 feet below surface the first week, 414 feet below surface the second and third week, and 5 feet below surface the fourth week); C, temperature of water at surface of lake at a station located in a boat anchored in the lake; D, temperature of air in shade of a building on the lake shore; E, wind velocity at margin of lake. Numbers at left indicate above temperature in Fahrenheit and below miles per hour of wind velocity. July 24-27 anemometer readings were not taken. It wasa period of very low wind and is indicated approximately by the dotted line. The University of Nebraska, Lincoln, Nebr. DEPARTMENT OF NOTES AND REVIEWS It is the purpose, in this department, to present from time to time brief original notes, both of methods of work and of results, by members of the Society. All mem- bers are invited to submit such items. In addition to these there will be given a few brief abstracts of recent work of more general interest to students and teachers. There will be no attempt to make these abstracts exhaustive. They will illustrate progress without attempting to define it, and will thus give to the teacher current illustrations, and to the isolated student suggestions of suitable fields of investigation.—[Editor.] LEECHES CONSIDERED AS OLIGOCHAETA MODIFIED FOR A PREDATORY LIFE Michaelsen (Mitt. Zool. Mus. XXXVI, Hamburg, 1919) was led to a study of the relationships between these two groups of animals, by noticing a figure in a recent paper on Sudanese Hirudinea. The figure represented an organ that was interpreted by the author, as a diverticulum of the alimentary tract of the leech, opening to the exterior on the mid-dorsal surface of the 13th somite. Similar organs have been described in certain leeches from Sumatra, in which they are paired, and the external pores are ventrally situated. The figured organ strongly resembles the spermathecae of certain oligo- chaete species in the families of Enchytraeidae and Lumbriculidae, in which the spermathecae communicate internally with the alimen- tary tract. Similar relations have also been found in certain species of other families of Oligochaeta. As a result of his studies, Michaelsen has reached the conclusion that the Hirudinea are, in reality, Lumbriculidae which have under- gone special modifications in adaptation to a predatory mode of life. He believes that such a conclusion receives much support from a careful comparison of the structure of two intermediate types of worms: the Branchiobdellidae, and Acanthobdella peledina Grube. The former are parasitic in the gill chambers and on parts of the surface of crawfishes, and, as their name indicates, were formerly included with leeches; but recently their closer relationship with the Oligochaeta is generally admitted. Acanthobdella peledina is a peculiar leech-like parasite of certain fishes of the genus Salmo, in northeastern Europe, and in western Siberia. On the ventral surface 86 NOTES AND REVIEWS 87 of several anterior somites, are paired bundles of setae, and the charac- ters of the reproductive organs and of the body cavity are also nearer to those of the Oligochaeta than to those of the leeches. Michaelsen concludes that, although there is some justification for including these two groups in the family Lumbriculidae, it is nevertheless preferable to recognize them as two distinct families of Oligochaeta, Branchiobdellidae and Acanthobdellidae closely related to the Lumbriculidae. After making this disposition of these two groups, the author makes a comparison of the various structural characters of the Hirudinea and Oligochaeta. Attention is called to the fact that there is a wide range of varia- tion among different representatives of the Oligochaeta, and that most of the characters which one is accustomed to think of as typical of the Oligochaeta are not present in all members of the group, though they may be in a majority of the better known ones. It is also shown that many of the characters of Hirudinea which one is likely to assume as distinguishing them from Oligochaeta, may be found present in certain members of the latter group. Absence of setae occurs in a genus of the oligochaete family Enchytraeidae, as well as in Branchiobdellidae, and they are greatly reduced in numbers and size in various other representatives. As previously mentioned, four pairs of well developed setae are present on each of several anter- ior somites in Acanthobdella peledina which has previously, without question, been assumed to belong to the Hirudinea. The shortened body and thickened body wall of the leeches, with a correlated reduction of the body cavity, are already forecast in Chaetogaster and in certain species of Lumbriculidae, to say nothing of the Branch- iobdellidae and Acanthobdella. They are natural accompaniments of a change of food, and assumption of a predatory mode of life. There is great variation in the structure of the nephridia among the Oligochaeta, and absence of ciliated nephrostomes and of cilia in the excretory part of the ducts is found in species of diverse groups. ‘The ventro-median position of the pores of the efferent ducts of the reproductive organs of leeches has a counterpart in certain species of Lumbriculidae and of the earthworm subfamily Eudrilinae. The most significant character which distinguishes the Hirudinea, in general, from the Oligochaeta, is the position of the spermaries 88 AMERICAN MICROSCOPICAL SOCIETY in somites posterior to the one which contains the ovaries. This relative position of the two kinds of gonads is the opposite of that normally found in Oligochaeta, and in the connecting forms, Branch- iobdellidae and Acanthobdella. To account for this reversal of rela- tions, the author refers to instances where Oligochaeta are found with a considerable number of consecutive somites containing gonads; and also to papers by different writers, in which gonads of certain oligochaete species have been shown to produce one kind of germ cells at one time, and at other times to produce those of the opposite kind. From individuals with series of gonads of this type, he thinks it not improbable that there may have been derived descendants in which the relative position of the gonads of the two sexes is in the reverse order from that of the ancestors. For details of structure and references to the literature involved in these comparisons, the original paper must be consulted. The author thinks it desirable to modify the outlines of classifica- tion, to fit these new views of relationship. He proposes a class Clitellata which is co-ordinate with the class Chaetopoda, and with three other classes which contain marine forms and are not involved. The class Clitellata includes two orders, Oligochaeta and Hirudinea; distinguished chiefly by the differences in the degree of development of the body cavity, and the relative order of the gonads. The class Chaetopoda includes two orders, Protochaeta and Polychaeta. FRANK SMITH Department of Zoology, Univ. of Illinois PROCEEDINGS OF THE AMERICAN MICROSCOP- ICAL SOCIETY MINUTES OF THE ST. Louis MEETING The thirty-eighth annual meeting of the American Microscopical Society was held in affiliation with the A.A.A.S. at St. Louis, Mo., Dec. 31, 1919. In the absence of President Griffin, Vice-President Whelpley acted as chairman. The report of the Treasurer for the years 1918 and 1919 was accepted and referred to an auditing committee composed of Professors H. B. Ward and H. J. VanCleave. The report of the Custodian was accepted, ordered printed, and referred to an auditing committee composed of Messrs. Edw. Pennock and Edw. P. Dolbey. A vote of appreciation was extended to Professor T. W. Galloway, the retiring Secretary, for a most valuable service rendered to the Society during the past ten years. The meeting voted approval of the action of the Executive Committee in appoint- ing Mr. Wm. F. Henderson as Treasurer, and Professor Paul S. Welch as Secretary at dates in advance of the regular annual business meeting. The following officers were duly nominated and elected for the constitutional periods: President, Professor T. W. Galloway, New York; First Vice-President, Chancey Juday, University of Wisconsin; Second Vice-President, Professor A. D. MacGillivray, University of Illinois; Secretary, Professor Paul S. Welch, University of Michigan; Treasurer, Mr. Wm. F. Henderson, James Millikin University. Professor Frank Smith of the University of Illinois, Professor J. E. Ackert of the Kansas State Agricultural College, and Dr. B. H. Ransom of the Bureau of Animal Industry were chosen as the elective members of the Executive Committee for 1920. Minutes of the last annual meeting were approved as printed. Adjourned. Pau S. WELCH, Secretary CUSTODIAN’S REPORT FOR THE YEARS 1918 AND 1919 SPENCER—TOLLES FUND Amount reported December 19075) 0) cc 60s os Fok aaa eaaee 533197 jmme.30; 1918 Dividendsreee ten. cerns Meee coer Gam eee 159.93 Dees Sl; 1918 Dividendseraree eres ee oa ticks cee eae 164.73 juners0: 1919) Divadendstemreaner se warts tee en ater heer eiays 226.24 Weerst 1919) MividendSeardyan eee ee ees ea isicheasciee 176.46) 12736 6058 .93 less Grant: Non Gas ce Mee eed enc cmaraorte 100 .00 Net amount invested ac cone ey a cee ea betes 8 5958 .93 Increase during last two years $627. 36. 89 90 AMERICAN MICROSCOPICAL SOCIETY TOTALS Alliicontributions 44°) Meee ee Ce eee eee 800.27 All Salesiofiransactionsenian aoe eee eee 878.38 AllcLigememberships sc0520 Sn ene cstaive mantels wants 300.00 AllinterestiaaDividendss sare eee eee eee eee 4270.28 LESS (AU Granta ene ste nine ee one tn Merten) 7 EOL aan 250.00 ALND uestior Ibitesmembersitsn5 ee ee oe eee 40.00 290.00 5958.93 Life members: (Robert Brown, dec’d.); J. Stanford Brown: Seth Bunker Capp; Harry B. Duncanson; A. H. Elliott; John Hatly. Contributors of $50 and over; John Aspinwall; Iron City Microscopical Society, Magnus Pflaum; Troy Scientific Society. (Signed) M. Priaum, Custodian. Philadelphia, Pa., January 10, 1920. The undersigned having examined the foregoing report certify that we find the amount invested as shown therein $5958 .93—correct, as shown by the Pass-Book of the Keystone State B. & L. Association, the same being brought down to the 2nd instant inclusive. (Signed) EDWARD PENNOCK, Epw. P. DoLBey, Auditing Committee. ANNUAL REPORT OF THE TREASURER OF THE AMERICAN MICROSCOPICAL SOCIETY DECEMBER 22, 1917 TO DECEMBER 21, 1918 RECEIPTS BalancetonyhandtromauditofA Olen ee eee ae eee $770.57 Membership) dues sites ees souls lees bt ee eee IE eh ee eee 548.84 Backivolumese ins te cedar aces oa ne ena eee As $ 34.84 FonwlO1gie ten fod tonnes ba vena Sob LoniNe At ae tia oe 226.00 Or AGI Oe Che bal tere eet ek ee APR kere ee LPT 286.00 Or dO20 se oti eerie een ae nesta er mperatMe eR oia ys 2.00 Subscriptionsars tie ene aes bila ee eRe settee trea ne eee nee $ 370.40 Backvolumestinsaey net ose ieee Soe ANE co $ 50.00 Wolume SOL xa eten mn come cate ce ns sehen ais Oh ay ae 95.00 Woltmers 7) tect Beato ies etetit eee ot Gp ee 140.20 Wolters eis heer asi sl, eran er VACahn Retr eels 83.20 VOLUME 73922550 ee aaa 1h le IR a eed 2.00 Unitiation wees ye ae eenee oh een ete ieee KO Cee tee ee $ 15.00 Advertisersvoltime3O/2iie ici. oe ees ee oe eee 55.00 SVOLUINIE RS AE ore ioeraic ooh Secs ee ee eR ee C ATE ee 120.00 SUDATIES Ay cocycle iemeaal yeaheah even azote kolo cA THOR ore RO ee DT ee 1.09 PROCEEDINGS OF AMERICAN MICROSCOPICAL SOCIETY 91 EXPENDITURES Publishing sPransactions., 4.504 oo cicli hese iehase chccepeiete aloe eran dies ayaa ated ao see $877.82 Volume S6):num ber Aes 5s ticeieietss x dace od aes se bagels $293.82 Volume:S7s number List yUe eo oe oa eal ating) ole 182.57 Volumersdamum ber: 2 iets cpects ain wa araitae laters 181.65 Volume 37, aiumibier, Seccccice sy ieioa or ceiererats erareetenaa(iang 171.05 PL atesty se ee he ere ee ate eho seats clcratsaehe orotate 48.73 Postage, ands Prpressianien ereersas ecise tial cove reel cais Sls cer a erate tate nea Tale cee $59.48 Oilice (Expeniseseprer gargs str 5s shel spavay sister lst el egaiists, 6) cho aha steerer ve el S528 Seerebanve ee ees cao uran es eter ann $23.17 TRL EASULOT pebehe ere so here lec eerste shemaene hae sicsree el meatah eters 12.10 Miscellaneous: itemise wastes Ascrsceiotetiticiarsier orcieruia a ai elaktye sia le laceiaceiatel etwas & 11.85 MT AT De PENUDE LURES ls) cisvoie eerie arse specs ena tens al tap ak eel orl $ 984.42 Balance’on hand sane eotcrc Sern etre Hae ee MUNA te et Ors sare ovarian Vans eiahalie level 896.48 $1,880.90 Respectfully submitted, H. J. VAN CLEAVE, Treasurer. REPORT OF OUTGOING TREASURER FOR THE PERIOD OF DEC. 22, 1918 TO FEB. 28, 1919 RECEIPTS Balagice Morag lamer se eee iis Fae LW) rhe Wiieda slaueheaseninis eu Mtarets a & $896.48 Menibarshyn dies estes vee eee ays ree hata c's ora ee arenas aeetaverets Hall dvs lah ace 72.00 BACK AV ONITEE Sener ymmon tes eters lee Mie tua) 5 sat analasakar Spt $10.00 BGOrp LOL Ope cerry Meek ee tort cele SU al a Ee 60.00 FOr 1920 eas enh eure Solara e ay Val elcce ed ler ate shale lets 2.00 SUDSCLIpPtONS . sae P Nea aera ce ceih ara oe eu apeiane ares vam anes 47.40 Back: volumestemp eerste neck Diag iels eine $ 4.00 Volume 3S neta etceraniaiins semnuinei i Waki kis Bebisr 41.00 Volume: 39 Sep eanrer ran waar iti tc ee can kia s/okr nem aang 2.40 Initia tion fees 15a ean eee ery er eta Se ae Weupy Seer oerii a Di Wa Ne As 9.00 AGvertisements! VOLUMES Tek eee te OR eS ce ened neal olaneboee 25.00 92 AMERICAN MICROSCOPICAL SOCIETY EXPENDITURES Publication of Transactions Volume 37, number 4..................... $267.14 Postage and iapressiss oS oa eco, HEN cele he hoe aes Me eee 25.26 Officexexpensesiy Mis.) Ne aeciesarse see Om eee ott El eee ee eae 23.96 ICCEEEARY, Sa. A'Sl oho icthie ate met ew lant eee CU ae eee $ 5.55 PDECASUTETS 245 fasts fio Wa Ses Ey TEA 18.41 Mirscellaneousty 335! maces, eee ee eee eee ee ee aE ee eee 3.50 TOTAL MSXPENDITURES ry teehee ie eet ee re $ 319.86 Balance transterreditoynewslneasurer-e pe) eee ee eee eee eee 730.02 $1,049.88 Respectfully submitted, H. J. Van CLeave, Treasurer. REPORT OF AUDITING COMMITTEE ON TREASURER’S ACCOUNTS FROM DECEMBER 22, 1917 TO FEBRUARY 28, 1919 This is to certify that we have this day examined the accounts of H. J. 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Warp FRANK SMITH Audit Committee. _ ANNUAL REPORT OF THE TREASURER OF THE AMERICAN MICROSCOPICAL SOCIETY March 1, 1919 to December 24, 1919 RECEIPTS Balancemeceived:irom) former treasurer. 4.6 eee eens ee oe eee ae $ 730.02 Dues)received tromVolume 3/7 orbefore.. 0. cee os sane aeeeiee 36.00 Dues received trom Wolumesonee ne eee eo oe cee eee EERE 108.00 IDwesireceiveduronlavolume 39s sae os tei ee ic eae asian aaa ee 292.10 Duesireceivedurom Volume 40S.) nlc aoe cy Bee ee eee 2.00 NTE ALIONUEES hc AA le Tee era ey Cae oreo ct ce See ae AL ae oe 66.00 Subscriptions for Volume: 37 ‘or before. .)-1= 2.2.65) o¢.nhie ie oes ecaseene 16.00 pubscriptions dor Welume 38.42.0220 42> bobs ahs as eases oe Oe eR Oer 51.80 Subscriptionsitor Volume 39 7i4. cctod i oa) 8o.cs Sica cn here ere ee 34.00 Sales of Transactions, duplicates and back numbers ...........--..--+5 183.00 Donation from T. B. Magath for aid in publishing his paper..........-.. 50.00 Advertising toravolumes' ss: ands30 er sears ane aac 55.00 PSTN Ys bg (ac Gan cae ALG tenn hn) ee eae MI AL RMS eA Pe ae Oe tae 4.50 PROCEEDINGS OF THE AMERICAN MICROSCOPICAL SOCIETY 93 EXPENDITURES Printing Transactions; Volume 38) NGIE yet ie eeoke o ak raters ttt $201.03 Printing ‘Transactions Volume38; Noi 2)... o7s,5 coves a nas os oe eee oe chase 265.21 Printing ransactions, Volume: 38) NO.tSic.. cis siege sale taste 2 eto tie asacal ahenene 337.47 Plates:for VolumersowNovar sitio ae eee homey ea sion eee nioraines 76.30 Printing yAuUthonriSexe prints arse cciye eheeeie cae arate eapste me eens cet 20.54 Postage ange hi xpressmoroecretarye sinners cts oat. alia eieie erator 73.92 Postage-andxpress for Ereasurer: 22 2J.)0c sslases aayrede aus cee ei ea 22.09 OMICe Expenses ON GecCrebanyy. ci. (ire sie olor niet eee aleyapeeeee cate mente ee 126.45 Office. expensestoielreasurenkn este 5 cs acta leith eo cree ee 19.70 SUNGVICS Ay rere Peer ie cree AS aie oa arentuNtcie, Role ee ae toca) ae el arc 5.67 Balancetonle bene ager ioe etal ra Cea ss. g atarer tise ti sacha aioraineaes wees loons 480.04 MNO TATH ORIN DITS Meee cn ier alree slayer edie vit Ns ean yt Cie pee $1,628.42 W. F. HENDERSON, Treasurer This is to certify that we have examined the books and vouchers of the Treasurer and find them to be in good condition and to give a correct record of moneys received and expended as indicated. Henry B. Warp H. J. VAN CLEAVE Auditing Committee March 24, 1920. TABLE OF CONTENTS For VoLUME XXXIX, Number 2, April, 1920 Modern Dark-field Microscopy and the History of its Development, by Simon IS ESTEIAE (CORZAS oie Geetehcene OS euch ONE oh SIE NC OCP OU ERCP R EOS Ue A New Bladder Fluke from the Frog, with Plate XIII, by John E. Guberlet Labeling Illustrations, with Plates XIV to XVII, by Z. P. Metcalf Notes and Reviews: Position of Micropterygidae; Micropterygidae; Filariasis in U. S.; Polyembryony and Sex; Origin and Significance of Metamorphosis 95 142 149 163 TRANSACTIONS OF American Microscopical Society (Published in Quarterly Instalments) Vol. XXXIX APRIL, 1920 No. 2 MODERN DARK-FIELD MICROSCOPY AND THE HISTORY OF ITS DEVELOPMENT BY Smmon Henry GAGE Professor of Histology and Embryology, Emeritus Cornell University INTRODUCTION In most work with the microscope the entire field of view is lighted and the objects to be studied appear as colored pictures or as shadows—in extreme cases, as silouhettes—on a white ground. As the field is always light, this has come to be known as Bright-Field Microscopy (Fig. 1). Fig. 1 Fig. 2 Bright- and dark-field photo-micrographs of the same objects (starch grains). In contrast with this is Dark-Field Microscopy in which the field is dark, and the objects appear as if they themselves emitted the light by which they are seen (Fig. 2). 96 SIMON HENRY GAGE The study of objects in a bright-field probably comprises 95% of all microscopic work, and is almost universally applicable. On the other hand dark-field microscopy has only limited applicability, and yet from the increased visibility given to many objects it is coming to be appreciated more and more. Definition.—In its comprehensive sense, Dark-Field Microscopy is the study of objects by the light which the objects themselves turn into the microscope, and none of the light from any outside source passes directly into the microscope as with bright-field microscopy. There are two principal cases: (A) The objects which are truly self-luminous like phosphorescent animals and plants; burning or incandescent objects, and fluorescent objects. (B) The objects which emit no light themselves, but which deflect the light reaching them from some outside source into the microscope. These two groups are well represented in Astronomy. If one looks into the sky on a cloudless night, the fixed stars show by the light which they themselves emit, but the moon and the planets appear by the light from the sun which they reflect to the earth, the sun itself being wholly invisible at the time. As there is rela- tively very little light coming from the intervening space between the stars and planets, all appear to be self-luminous objects in a dark field. This reference to the sky at night will serve to bring out two other points with great clearness: (1) The enhanced visibility. Everybody knows that there are as many stars in the sky in the day- time as at night, but they are blotted out, so to speak, by the flood of direct light from the sun in the daytime, while at night when these direct rays are absent and no light comes from the back-ground the stars and the planets show again by the relatively feeble light which they send to the earth. (2) The other point is that in dark-field microscopy the objects must be scattered, not covering the whole field (Fig. 2). If there were no intervening empty space the whole face of the sky would look bright It will b’e seen from this that ordinary sections or other objects so large that they fill the whole field of the microscope cannot be studied advantageously by the dark-field method, for they would make the whole field bright. But for the liquids of the body, blood, lymph, synovial, and serous fluids, fluid from the cavities of the MODERN DARK-FIELD MICROSCOPY 97 nervous system, saliva, and all other mucous fluids, and isolated tissue elements where the solid or semi-solid substances are distrib- uted in a liquid, the appearances given by this method are a revela- tion as was pointed out by Wenham and Edmunds and many others over fifty years ago. No less is the revelation coming from the study of bacteria, protozoa and other micro-organisms in the dark field. DARK-FIELD AND ULTRA-MICROSCOPY In both of these the objects seem to be self-luminous in a dark field, and no light reaches the eye directly from an outside source, but only as sent to the eye from the objects under observation. The terms simply represent two steps, and merge into each other. Dark-Field Microscopy deals with relatively large objects, 0.24 or more in diameter, that is, those which come within the resolving power of the microscope. Ultra-Microscopy deals with objects so small that they do not show as objects with details, but one infers their presence by the points of light which they turn into the microscope. This can be made clear by an easily tried-naked-eye observation. Suppose one is in a dark room, and a minute beam of brilliant light like sunlight or arc light is directed into the room. Unless one is in the path of this beam of light it will remain invisible, but if there are vapor or dust particles present they will deflect some of the light toward the eye and will appear as shining points. The character of the particles cannot be made out, but the points of light they reflect indicate their presence. As Tyndall used this method in determining whether a room was free from dust in his experiments in spontaneous generation, the appearance of the shining dust particles is sometimes called the “Tyndall effect.” The two forms are said to merge, because in studying objects like saliva, etc., with the microscope designed especially for dark-field work, some of the objects seen will show details, but some are so small that they show simple as points of light usually in the form of so-called diffraction discs. The larger objects in the saliva come in the province of dark-field microscopy, and the smallest ones, of ultra-microscopy, and in this case the instrument used might with equal propriety be called a dark-field or an ultra-microscope. The great purpose of the dark-field microscope is to render minute objects or details of large objects plainer or actually visible 98 SIMON HENRY GAGE from the advantages offered by the contrast given between the brightly lighted objects and the dark background. For example, with the homogeneous immersion objective the study of fresh blood with the ordinary bright-field method enables one to see the red corpuscles with satisfaction, but the leucocytes are not easily found and the blood-dust (chylomicrons) and the fibrin filaments are not seen at all or very faintly. With the same microscope using the dark-field illumination the leucocytes are truly white cells, and the blood-dust is one of the striking features of the preparation, and the fibrin filaments seem like a delicate cobweb. In this connection, perhaps a few words should be added on the terms Resolution and Visibility. Both came over from the ancient science of astronomy, and are properly used only when restricted as in astronomy. By resolution is meant the seeing of two things as two, not blended. For example if two stars are close together they are re- solved if they appear as two. When the telescope was invented it was found that many stars that appeared single were really two stars close together. Iftwo lines are placed close together they appear as two to the naked eye when close up, but as one moves away the lines seem to fuse and make one. Visibility refers only to the possibility of seeing a thing. In the above examples the twin stars were visible to the naked eye but not resolved into two, and likewise the lines were long visible after they could be seen as two lines. Now the purpose of the ultra-microscope is solely to increase the visibility of small particles without reference to their details of structure. Dark-field microscopy, on the other hand, while it gives greatly increased visibility, also gives resolution of details. As with bright-field microscopy the resolution of details of struc- ture depends directly upon the numerical aperture (NA) of the objective, and the brightness upon the square of the aperture (NA?). METHOD OF DARK-FIELD MICROSCOPY In this article the ultramicroscope and the study of self-luminous objects will not be further considered, but the discussion will be limited to objects which must be lighted by some outside source. There are two principal cases: (1) objects which are lighted from above the stage of the microscope or by so-called direct light (Fig. 3) MODERN DARK-FIELD MICROSCOPY 99 and, (2) objects which are lighted from below the stage, or by trans- mitted light (Fig. 4). Fig. 3. Light from above the stage. (From The Microscope) In both cases the light from the source is at such an angle that none of it can enter the objective directly but only as it is deflected or “radiated” by the objects in the microscopic field. “| Objective Stage SAMARAS Fig. 4. Light from below the stage. When the light upon the object is from above the stage the back- ground must be non-reflecting. If the background were white there would be a kind of bright-field, not dark-field microscopy. The black-background is secured either by placing the object directly upon some black velvet or other non-reflecting surface, or on a glass slide which in turn is placed upon black velvet, etc., or on a dark well. The simplest way to produce a dark-well is to turn the condenser aside and place a piece of black velvet over the foot of the microscope. Or the condenser can be lowered well and the velvet put over the top of the condenser. 100 SIMON HENRY GAGE Diffuse daylight from a window, or more satisfactorily, artificial light directed by a mirror or lens (bull’s eye),is directed obliquely down upon the preparation (Fig. 3). Exactly the same preparation will answer for light from below the stage. In this case the condenser is turned out of the way, and some black-velvet put over the foot of the microscope to cut out stray light. For a good naked eye demonstration showing the increased visibility due to the dark-field, some cotton may be placed on a piece of black velvet, and a similar tuft of cotton on a white card. For the special methods of lighting microscopic objects from above the stage, see in the historical summary at the end of this paper. Dark-Field Microscopy by Transmitted Light—To make objects appear self-luminous in a dark field when illuminated by beams of light from below the stage, two things are necessary: (1) The objects must be able to deflect in some way the light impinging upon them into the microscope. (2) None of the light from the source must be allowed to pass directly into the microscope. These conditions are met when (a) the objects to be studied are of different refractive index from the medium in which they are mounted, and (b) when the transmitted light thrown upon the object is at such an angle that it falls wholly outside the aperture of the objective (Fig. 4-7). The objects deflect the light into the microscope (1) By Reflection (2) By Refraction (3) By Diffraction Any one of these will suffice, but any two or all of the ways may be combined in any given case. For low powers where the aperture of the microscope objective is relatively small it is comparatively easy to make the transmitted beam of so great an angle that none of it can pass directly into the microscope. A simple experiment will show this: A 16 mm. or lower objective is used, the substage condenser is turned aside and on the stage is placed a clean slide with a little starch, flour, or other white powder dusted upon it. If now the mirror is turned to throw the light directly up into the microscope the field will be bright and the objects relatively dark, but if the mirror is turned at an angle suf- MODERN DARK-FIELD MICROSCOPY 101 ficient to throw the whole beam at a greater angle than the aperture of the objective will receive, the field wiil become dark and the starch or flour grains will stand out as if shining by their own light. If some black velvet is placed on the foot of the microscope so no light can be reflected upward into the microscope from the foot or the table, the field will be darker. This experiment succeeds by either natural or artificial light. If some water containing para- mecium and other micro-organisms is put on the slide and put under the microscope, the organisms will appear bright and seem to be swimming in black ink. It is readily seen that with the method just discussed the light is all from one side (Fig. 4). To light the objects from all sides, that is, with a ring of light, the simplest method, and the method utilized in all modern dark-field microscopy, is to use a hollow cone of light, the rays in the shell of light all being at so great an angle with the optic axis of the objective that none of them can enter the microscope directly (Fig. 4-7). With Refracting Condensers. With the condensers of the achro- matic or chromatic type used for bright-field microscopy a solid cone of rays is used. To get the dark-field effect the objects to be studied must be lighted only by the rays at so great an angle that they cannot enter the objective directly. This requires that the condenser shall have a considerably greater aperture than the objec- tive. The ordinary method of making the hollow cone is to insert a dark stop—central stop—to block or shut off the central part of the solid cone of light. The object is then illuminated with a ring of light of an aperture greater than that of the objective (Fig. 6). Some of this light is turned by the objects into the microscope. As only a relatively small amount of the light is deflected by the objects into the microscope, it is evident that there must be a great deal of light to start with or there will not be enough passing from the object to the microscope to make it properly visible. The question also naturally arises how one is to determine the size of the central stop to be used with any given condenser and objective. This is easily determined as follows: The field is lighted well as for ordinary bright-field observation and some object is got in focus. Then the object is removed and the iris diaphragm of the condenser opened to the fullest éxtent. If one then removes the ocular and looks down the tube of the microscope and slowly closes 102 SIMON HENRY GAGE the iris, when the full aperture of the objective is reached, that is, when the back lens of the objective is just filled with light, the opening in the iris represents the size of the central stop to use to cut out all the light which would pass into the microscope from the condenser; all the ring of light outside of this is of too great an angle for the aperture of the objective. One can measure the size of the opening in the iris with dividers and then prepare a central stop diaphragm. Fig. 5. Ordinary condenser with sectional and face views of the central stop (D). (From The Microscope) A visiting card is good for this. It should be blackened with India ink. To be on the safe side it is wise to make the central stop a little greater in diameter than the iris opening (Fig. 5). If now the microscope is lighted as brilliantly as possible, and then the iris opened to its full extent and the blackened central stop is put in the ring under the condenser, and a slide used with starch or flour on it, the flour or starch particles will be lighted with the ring of light, and they will deflect enough into the objective to make the objects appear bright as if shining by their own light, the background remaining dark. If the field looks gray or light instead of black it is because the central stop is too small or not centered or the particles used for objects are too numerous, not leaving enough blank space. MODERN DARK-FIELD MICROSCOPY 103 One can determine what is at fault thus: The ocular is removed. If the central stop is too small the back lens of the objective will show a ring of light around the outside. If the central stop is not centered there will be a meniscus of light on one side. If the objects are too numerous the whole field will be bright. To verify these statements one can use a specimen with flour or starch all over the slide. It will look dazzlingly light, with the ocular in place and the back-lens will be very bright when the ocular is removed. For the meniscus of light when the central stop is decentered, purposely pull the ring holding the stop slightly to one side and the meniscus will appear in the back lens. To show the ring of light due to a too small size of the stop, the easiest way is to use a higher objective, say one of 3 or 4 mm. in place of the 16 mm. objective. While it is necessary to eliminate all the light which could enter the objective directly, the thicker the ring of light which remains to illuminate the objects the more brilliantly self-luminous will they appear, therefore one uses only the stop necessary for a given objec- tive. If one makes central stops for the different objectives as described above it will be greatly =mphasized that the objectives differ in aperture, in general the higher the power the greater the aperture, and consequently the larger must be the central stop, and the thinner the ring of light left to illuminate the object. As one needs more light for high powers instead of less than for low powers, the deficiency of light caused by the large central stop must be made good by using a more brilliant source of light for the high powers. Reflecting Condensers. As was first pointed out by Wenham, 1850-1856, refracting condensers are not so well adapted for obtaining the best ring of light for dark-field work as a reflecting condenser, on account of the difficulty in getting rid of the spherical and chromatic aberration in the refracted bundles of such great aperture. He first (1850) used a silvered paraboloid and later (1856) one of solid glass as is now used. Within the last 10-15 years there has also been worked out reflecting condensers on the cardioid principle. The purpose of all forms is to give a ring of light which shall be of great aperture, and be as free as possible from chromatic and spherical aberration, and hence will form a sharp focus of the hollow cone upon the level where the objects are situated. 104 SIMON HENRY GAGE “Glass. Slide S AM SSSSET TST LLLEET TT LLL LLL LLL rd Centrai Stop Fig. 6. Bright-field condenser with central stop to give dark-field illumination. This is a sectional view showing the hollow cone of light focusing on the object and then continuing wholly outside the aperture of the objective. The light deflected by the object into the objective is represented by broken lines. The glass slide is in homogeneous contact with the top of the condenser, and the medium beyond the object is represented as homogeneous with glass. Centre! Stop Fig. 7. Paraboloid condenser for dark-field illumination. Axis—The principal optic axis of the microscope. Central Stop—The opaque stop to cut out all light that would be at an aperture less than 1.00 NA. MODERN DARK-FIELD MICROSCOPY 105 Cover Glass—The cover for the object. For dry objectives it must conform to the objective, and with homogeneous objectives it must be less than their working distance in thickness. C r-—Face view of the top of the paraboloid showing the centering ring, the spot of white ink in the middle and the grains of starch for centering and focusing high powers. Glass Slide—The slip of glass on which the object is mounted. It is connected with the top of the paraboloid by homogeneous liquid, and must be of a thickness to permit the focusing of the hollow cone of light upon the object. Hi, Hi—Homogeneous liquid between the cover-glass and the objective and between the top of the condenser and the slide. NA 1.00 to 1.40—The numerical aperture of the hollow cone of light focused on the object by the paraboloid. As indicated on the left this is represented by a glass angle of 41 to 67 degrees. 41° 67°—The limits of the angle of the rays in glass. Objective—The front lens of the objective. The light rays deflected by the object are indicated by white lines below and through the lens, then by broken, black lines above the front lens of the objective. Water—The mounting medium for the objects. In this diagram the course of the rays from the paraboloid are indicated as if the objects were mounted in homogeneous liquid and that the rays passed beyond the focus into a medium homogeneous with glass. TABLE SHOWING THE Maxtuum ANGLE IN GLASS, AND THE CORRESPONDING NUMERICAL APERTURE OF THE LIGHT WHICH CAN Pass INTO MEDIA OF DIFFERENT REFRACTIVE INDEX ABOVE THE CONDENSER (Fic. 8-11) Angle in Numerical Index of Glass Aperture Refraction HewAirover the condenser. 22.402 25...-4. 41° 1.00 1.00 DAV ALGI Nea fey. caiman snippet Gi Sen gtaeet 61° 133 1.33 © SLOSS a eee eee Ot ema a 75° 15! 1.47 1.47 4° Homogeneous liquid. :.).......0..2..- 90° 1.52 1.52 In the reflecting as in the refracting condensers the central part of the light beam from the source is blocked out by a central stop and only a ring of light enters the condenser. Immersion connection of condenser and glass slide bearing the specimen.—While the purpose of the reflecting condenser is to pro- duce a very oblique beam of light for illuminating the objects, it is seen at once that the laws of refraction will prevent the light from passing from the condenser to the object unless the glass slide bearing the object is in immersion contact with the top of the condenser. 106 SIMON HENRY GAGE That is, for air (index 1.00) above the condenser, the rays in glass at 41°, NA 1.00 and less can pass from the condenser into the air and expand into a hemisphere of light in it (Fig. 8). Rays above 41° are totally reflected back into the condenser. For water (index 1.33) above the condenser, rays in the glass at 61°, NA 1.33, and less can pass into the overlying water and make a complete hemisphere of light in it (Fig. 9). Rays above 61° are totally reflected back into the condenser. For glycerin (index 1.47) above the condenser, rays in the glass at 75° 151, NA 1.47 and less can pass from the glass into the over- lying glycerin and form a hemisphere of light in it (Fig. 10). All rays at a greater angle are reflected back into the condenser. For homogeneous liquid (index 1.52) over the condenser, there is no limit to the angle of light that can pass from the condenser to it (Fig. 11). Immersion Liquid between Condenser and Glass Slide. While water or glycerin answers fairly well it is recommended that homo- geneous liquid be used in all cases. At first glance this would seem unnecessary for, as just stated the aperture of the light is limited by the medium of least refractive index between the condenser and the object. Thus objects mounted in watery fluids, and especially those mounted in air would seem to have the illuminating ray that could reach them limited by an aperture of 1.33 in one case and of 1.00 in the other (glass angles of 61° and 41°). This would be true if the objects were suspended in the water or in the air, but many of the particles are not suspended but rest on the glass slide, that is are in so-called optical contact with the slide. This being true, the angle of the light which can pass from the condenser to them depends upon their own refractive index, and not upon that of the mounting medium (air or water). This explains also why objects not in optical contact with the slide are rendered more visible by the homogeneous immersion contact of slide and condenser for the scattered light from the particles in optical contact helps to light up particles not in contact. Another consideration also favors the use of the homogeneous immersion contact of slide and condenser, even for objects mounted in air. Physicists have found (see Wood) that beyond the critical angle, while all light is turned back into the denser medium, it does nevertheless pass one or more wave lengths into the rarer medium to MODERN DARK-FIELD MICROSCOPY 107 find, so to speak, an easier place to turn around in. If now any object is near enough the slide to fall into this turning distance of the totally reflected light it may be said to be in optical contact, and the light which meets it will pass into it instead of being totally reflected. Fig. 8, 9, 10, 11. Diagrams showing the angle and numerical aperture of the light in glass to fill the entire hemisphere above, with overlying media of air, water, glycerin, or homogeneous immersion liquid. As shown by the diagrams, the NA of the light in each case must equal the index of refraction (Ir) of the overlying medium to fill the overlying hemisphere with light. If the light is at a greater than the critical angle it is reflected back into the condenser. Such light is represented by black in 8, 9, 10. With homogeneous liquid (Hom. imr) above the condenser there is no critical angle. It should be said in passing that the medium of least refractive index in the path of the light beam from the condenser determines the critical angle at which the light is wholly reflected, and hence determines the maximum angle of the illuminating pencil that can light the object, but this does not apply if the object is in optical contact with the glass (see below). One can make a very convincing experiment to show the impor- tance of remembering that some of the objects are in optical contact with the glass slide and hence may utilize light which could not pass 108 SIMON HENRY GAGE into the surrounding medium. If the upper face of the dark-field condenser is cleaned as perfectly as possible, and then lighted well, one can see no light emerging from the top except where the centering ring is situated or where there are some accidental scratches. If one dusts some starch, flour or other white powder on the clean surface, the particles which make optical contact with the glass will glow as if self-luminous. In case one wishes further evidence, the end of the condenser should be carefully cleaned, and a glass slide of the proper thickness connected with it by means of homogeneous liquid, then some flour or starch can be dusted on the slide and it will glow as did the particles on the top of the condenser. These demonstrations show well with the naked eye and with objectives up to 8 mm. (Fig. 7, Cr.) Aperture of the Ring of Light in the Condenser. As the angle of the light illuminating the objects must be greater than can enter the objective employed it follows that the central part of the illuminating beam must be blocked out up to or beyond the aperture of the objec- tive to be used. The greatest aperture rays possibly attainable depends upon the opticians ability to so design and construct the condenser that it will bring the remaining shell or ring of light to a focus. For those designed to be used with all powers, the aperture of this ring of light usually falls between 1.00 NA and 1.40 NA. As water and homogeneous immersion objectives have a numerical aperture greater than 1.00 NA. it follows that they could not be used for dark-field observation with their full aperture, because much of the light from the condenser could enter the objective, giving rise to a bright or at least a gray field. Reducing diaphragms for high apertured objectives. As the lower limit in aperture of dark-field condensers is 1.00 NA, and sometimes even lower, it follows that a condenser for use with all objectives requires that none of them have an aperture over 1.00 NA. As all modern immersion objectives have an aperture greater than 1.00 NA, this aperture must be reduced by inserting a diaphragm in the objective. The general law that the resolution varies directly with the aper- ture, and the brilliancy as the square of the aperture, holds with dark-field as with bright-field microscopy. In order to determine by actual experiment with various dark-field condensers the best aperture of the diaphragm to select, the writer requested, the Bausch & Lomb Optical Company and the Spencer Lens Company to supply MODERN DARK-FIELD MICROSCOPY 109 reducing diaphragms for their fluorite, homogeneous immersion objectives ranging from 0.50 NA. to 0.95 NA. As measured by me these diaphragms ranged from slightly above 0.50 NA, to 0.97 NA. These varying apertures were tested on each condenser, using the same light and as nearly as possible identical preparations (i.e., fresh blood mounted on slides of the proper thickness). It seemed to the SS yy ag BSS Fig. 12. Large aperture objective with diaphragm to reduce the aperture to less than 1.00 NA. (From Chamot) D Funnel-shaped reducing diaphragm in the interior of the objective above the back lens. writer that the law of aperture as stated above held rigidly. The question then is, which aperture shall be chosen if but one diaphragm is available? It seemed to the writer that the one of 0.80 NA should be chosen, at least for these fluorite objectives. If three are to be had the range should be 0.70, 0.80 and 0.90. The reason why one over 0.90 is not recommended is because some examples of the best of the dark-field condensers tested, seemed to have their lower limit somewhat below 1.00 NA, and hence the field could not be made completely dark with the diaphragm of 0.97 NA. With others, however, the field was as dark with this large aperture as with the lower apertured diaphragms. A considerable range of reducing diaphragms for the homogeneous immersion objectives is recommended because all experience brings home to the worker with the microscope the conviction that some structures show better with the lower apertures and some with higher ones, and it is believed from considerable experience that the same fundamental principles hold in dark-field as in bright-field microscopy. 110 SIMON HENRY GAGE LIGHTING FOR DARK-FIELD MICROSCOPY As is almost self-evident, only a very small amount of the light passing through the condenser to the objects is deflected by the objects into the microscope, consequently the source of light must be of great brilliancy or there will not be enough to give sufficient light to render the minute details of the objects visible, when high powers are used. This visibility of minute details involves three things: (1) The aperture of the objectives; (2) The aperture of the illuminat- ing pencil; (3) The intensity of the light. The most powerful light is full sunlight. Following this is the direct current arc, the alternating current arc and then the glowing filament of the gas-filled or Mazda lamps. The reflecting condensers are designed for parallel beams con- sequently the direct sunlight can be reflected into the condenser with the plane mirror of the microscope. If the arc lamp, a Mazda lamp, or any other artificial source is used a parallelizing system must be employed. ‘The simplest and one of the most efficient is a plano- convex lens of about 60 to 80 mm. focus with the plane side next the light and the convex side toward the microscope mirror (Fig. 14) i.e., In position of least aberration. This is placed at about its principal focal distance from the source whether that be arc lamp, Mazda lamp, or any other source and the issuing beam will be of approximately parallel rays. These can then be reflected up into the dark-field condenser with the plane mirror. LAMPS FOR DARK-FIELD MICROSCOPY Up to the present the small arc lamp (Fig. 13), using 4 to 6 amperes is practically the only one considered really satisfactory. There is no question of the excellence of the direct current arc. The alternating current arc has two equally bright craters which renders its use somewhat more difficult. For most of the work in biology the arc gives more light than is comfortable to the eyes; but a still greater objection is that with the burning away of the carbons the source of light is constantly shifting its position, and hence the quality of the light varies from minute to minute. A third difficulty for hand-feed lamps is that one must stop observation frequently to adjust the carbons. MODERN DARK-FIELD MICROSCOPY 111 In spite of all these difficulties, however, the arc lamp is indis- pensable if one desires to attack all the problems for which the dark- field microscope is available. Fig. 13. Small arc lamp for dark-field illumination (From Optic Projection) This figure is to show the wiring necessary and the arrangement of the arc and lens to give a parallel beam. A—Heavy base of the lamp support. By means of a clamp the lamp can be fixed at any desired vertical height. HC and VC, the horizontal and vertical carbons. The HC must be made positive. F, the wheels by which the carbons are fed. TC—tThe tube containing the condenser. The condenser in the inner tube can be moved back and forth to get a parallel beam. Sh, black shield, see E. E—Black shield at the end of the lamp tube (Sh). It serves to screen the eyes and to show when the spot of light is thrown back by the mirror into the parallelizing lens. W1, W2, W3, W4—The wires of the circuit passing from supply to the upper carbon (HC) and from the lower carbon (VC) to the rheostat, and from the rheostat back to the supply in W1. Never try to use an arc lamp without inserting a rheostat in the circuit. As shown, it forms a part of one wire. It makes no difference whether it is in the wire going to the upper or to the lower carbon, but it must be in one of them. 6-Volt Headlight Lamp.—Next to the arc lamp in excellence for dark-field work is the 6-volt gas-filled headlight lamp (Fig. 14). The reason of this excellence is that the filament giving the light is in a very close and small spiral not much larger than the crater of the small arc lamp, and hence approximates a point source of light. 112 SIMON HENRY GAGE The brilliancy is also very great as the filament is at about 2800° absolute. The two sizes that have been found most useful by the writer are the bulbs of 72 watts and those of 108 watts. For the bulb of 108 watts a mogul socket is essential; for the 72 watt bulb the ordinary socket is used. Ve HN Cocty777770) Fig. 14. Diagram of headlight lamp and transformer for dark-field illumination (About one-sixth natural size). Axis—Axis of the parallel beam from the lens (L). Lamp—The 6-volt, 108 watt headlight lamp with its very small, close filament centered to the axis of the lens. It is in a mogul socket (ms) and can be centered vertically and horizontally by the inner and outer tubes and set screw (it, ot, s), and the brass slide (sl). Lamp House—The metal container for the lamp. (bb) Bafle plates near the bottom to help avoid stray light. At the left over the lens (L) is the sloping eye shade. L D G—Parallelizing lens cemented to polished daylight glass. Lamp wires—The large wires from the transformer (Transf.) to the lamp (Double heater wires are good). m c—Mistakeless connection between the lamp wires and the transformer (Transf). This is a Manhattan stage connector, and is different from anything else in the laboratory and therefore the lamp can never be connected with a 110 volt cir- cuit and burn out the lamp. Of course any other wholly different connection would answer just as well. Transf.—Diagram of a step-down transformer. As there are 18 coils around the soft iron ring on the Primary (P) or 110 volt side, and but one coil around the Secondary (S) side, the voltage is stepped down 18 times, or from 110 to 6 volts. In an actual transformer the coils would be far more numerous, but in this proportion. If the transformer were connected wrongly, i.e., with the lamp wires connected with MODERN DARK-FIELD MICROSCOPY 113 the primary (P) side, and the 110 volt supply with the secondary (S) side, it would then be a step-up transformer, and raise the 110 volts 18 times—with disastrous results. C, separable connection for the 110 volt supply wires. The only difficulty with these lamps is that as they are for a 6 volt circuit it is necessary to use a step-down transformer if one has an alternating current with a voltage of 110 or of 220, as is usual. If one has a direct current of 110 or 220 voltage, then it is neces- sary to use a storage battery, in general like those used for the lighting and ignition systems of automobiles. As a transformer uses up but a very small amount of energy it will be readily seen that in stepping down the voltage the amperage is correspondingly raised from the general law that the wattage is the product of the voltage into the amperage, and knowing any two the third may readily be found. For example with the 72 watt lamp, if the voltage is 6 the amper- age must be 72/6 or 12 amperes. With the 108 watt bulb the amperage must be 108/6=18 amperes. The heating of the filament is determined by the amperage, and also it must be remembered that the conductor of an electric current must be increased in due proportion for an increased amperage, con- sequently in the transformer the wires joining the 110 volt line is small because a very small amperage is necessary to give a large wattage; while from the transformer to the lamp the conducting wires must be large, to carry without heating the amperage necessary with the low voltage (6) to give the large wattage (108 or 72). For the 18 amperes of the 108 watt bulb, the Fire Underwriters specifications call for wire of No. 12 or No. 14 Brown and Sharp Guage, i.e., wire 1.6 to 2 mm. in diameter or a cable composed of smaller wire having the same conductivity. This specification is for continuous service. In wiring the headlight lamp from the trans- former, so called heater cable is good, provided one uses a double cable, that is the entire cable for each wire. ‘This is easily done by removing the insulation at the ends and twisting the two strands together, then it can be treated as one wire and the two thus treated used to join the lamp to the mistakeless connection (mc, Fig. 14, 15) of the transformer. As the resistance is small in these large con- ductors the full effect of the current remains to make especially brilliant the glowing lamp filament, and brilliancy is what is needed for this work. 114 SIMON HENRY GAGE It should be stated that the transformer for this purpose should be substantial and adapted to continuous service. It is known as a “Bell Transformer”’ as it is connected to ordinary house light systems for ringing door bells. The one used by the writer was obtained from the General Electric Co. in 1920 and costs at present seven dollars. It is marked: Transformer, type N D, Form P Volts 110 6. Capacity 108 KV-A, Cycles 60, Without taps in Primary.”’ (For making the connections, see the explanation of Fig. 14.) In comparing the two 6 volt lamps for dark-field work, the 72 watt lamp answers well for most purposes, but the 108 watt one approximates more nearly to the small arc lamp and is sufficient for probably 99% of all dark-field observation in biology. For the remaining 1% one could safely depend on sunlight. Siereopticon and Mazda lamps for dark-field. In absence of the head-light lamps described above, one can get good results by using in the lamp-house (Fig. 14-15), a stereopticon lamp bulb of 100 to 25@ watts. These bulbs have the filament arranged in a kind of ball, and hence fairly well concentrated. This filament must be centered with the parallelizing lens as described for the headlight bulbs. For the horizontal position, move the lamp back and forth by the brass slide until the front of the ball filament is in focus on the 10- meter screen. The microscope should then be placed from 15-25 cm. from the lamp-house. The rest of the procedure is exactly as for the headlight lamp. If one has neither headlight lamp nor stereopticon lamp, still good work can be done in biology by using the Mazda C bulbs where the filament is in the form of a loop or C. This is centered and focused as for the other lamps (Fig. 18). If one has only a lamp similar to Fig. 18, the daylight glass can be removed and the micro- scope placed close to the lamp. Fairly good results can be obtained with a 100 watt mazda stereopticon or c bulb without a parallelizing lens. The Spencer Lens Company recommend in addition to the small arc lamp, their small magic lantern (No. 394). This has either a 250 or a 400 watt stereopticon lamp bulb, and for parallelizing system, the two plano-convex lenses common with simple magic lanterns. The projection objective of the magic lantern is removed. This yields good results especially when a piece of clear daylight glass MODERN DARK-FIELD MICROSCOPY 115 is placed over the end of the cone left vacant by the removal of the objective. A real advantage possessed by these different lights is that the lamps are connected directly with the 110 volt circuit, no transformer being required, as with the headlight lamps. But if one is to do much dark-field work the headlight lamps are much to be preferred. Daylight effects with the headlight or Mazda lamps. For dark-field work as for work with the bright field, daylight effects are of the greatest advantage both for eye comfort and for the clearness with which details can be made out. The daylight effect is readily ob- tained by using a piece of daylight glass polished on both sides and cemented to the flat face of the parallelizing lens by means of Canada balsam (Fig. 14-15). ] \ Supply ||Tranef wires Fig. 15. Headlight lamp in its metal house, and the step-down transformer. (About one-eighth natural size) D. Glass—The window of daylight glass on the side of the lamp-house to be used for bright-field work. With the glass removed the centering of the lamp is facilitated. P. lens—Parallelizing lens of about 75 mm. focus. It is cemented to a piece of polished daylight glass. m c—Mistakeless connection between the lamp wires and the transformer (Transf.). Such a connection prevents joining the lamp with the 110 volt circuit, and thus burning it out. This cannot be connected wrongly. Transf.—Step-down transformer from 110 to 6 volts. Lamp-House with centering arrangement. To avoid the non- utilized light, and to place the source of light in the most favorable position, there must be an opaque box to enclose and support the head-light or Mazda lamp. As the filament giving the light must be in the optic axis and practically in the focus of the parallelizing 116 SIMON HENRY GAGE lens, the lamp or the lens must be sufficiently movable to attain the end. In the lamp-house here figured (Fig. 14, 15) the lens is stationary and the lamp is movable horizontally and vertically, that is, it can be raised and lowered and moved toward and from the lens in the optic axis. For the most perfect centering there should also be arrange- ments for moving the lamp or the lens from side to side. In the one here shown the parallelizing lens can be shifted slightly to take care of the lateral centering. Centering the Lamp-filament. As stated above the lamp-filament must be centered, that is, put in the principal optic axis of the paral- lelizing lens. This is most satisfactorily done by putting the paral- lelizing lens in position in the lamp-house and measuring the distance from the table to the middle point of the lens. The middle point of lamp filament should be placed at the same height from the table. This is easily accomplished by using the side window of the lamp- house and raising and lowering the lamp by means of the vertical adjustment (Fig. 14-15) until the filament is at the right height to be on the level of the optic axis. Then the lamp is turned until the spiral filament faces the lens. The two limbs of the fork holding the filament then face sidewise. Of course, they would make a shadow if they faced the lens. To get a parallel beam. ‘The most satisfactory way of doing this is to work at night or ina dark room. Having a white wall or white screen at about 10 meters distant, light the lamp and move it back and forth in the optic axis by means of the top slide (Fig. 14 sl) until the filament of the lamp is in focus on the screen, the filament will then be at about the principal focus of the parallelizing lens, that is, in a position to give approximately parallel light to the microscope. It is well to mark the position on the top of the lamp-house so that if it gets accidentally displaced it can be returned without trouble. It may be said in passing that the lamps are not all exactly alike so that when a new lamp is installed it is necessary to center and focus all over again. Focusing the crater of the small arc lamp. The makers arrange the carbons and the lens tube so that the crater will be approximately in the optic axis (Fig. 13). Now to get the crater in the focus of the parallelizing lens one can proceed in principle as with the headlight lamp. In the arc lamp, the carbons are fixed and the lens movable. Work at night or in a dark room and with the lighted arc move the MODERN DARK-FIELD MICROSCOPY 117 lens back and forth until there is a sharp image of the crater on the 10-meter screen. Lighting the Microscope. Assuming that the lamp filament or the crater of the arc lamp is centered with the parallelizing lens, one can find the best position for the microscope by holding some thick white paper in the path of the beam and slowly moving out along the beam. Where the spot of light is brightest and most uniform is the best place for the microscope mirror. With the headlight lamps and the arc light this is usually 20-30 cm. from the parallelizing lens. To get the spot of light to fall on the 45° mirror properly, the center of the mirror must be at the level of the axis of the beam. This can be brought about either by raising the microscope on a block, by inclining the microscope, or by tipping the lamp-house over toward the microscope. If some white paper is put over the mirror one can tell easily when the cylinder of light falls upon it. To get the light up through the condenser and into the objective it is necessary to so tip the mirror that an image of the source of light is directed back into the parallelizing lens. This image is reflected back from the flat top of the condenser to the mirror. With this arrangement of the mirror the microscope is almost always well lighted, and the mirror will need but a slight adjustment to give the best possible light. This will only be true however, when the source of light is centered to the parallelizing lens and the condenser to the axis of the microscope. This method of lighting the microscope saves much time and worry. It is effective with the microscope vertical or inclined, with the lamp-house vertical or inclined, and finally it is unnecessary to have the microscope in line with the beam of light. It may be at right angles or at any angle provided the beam of light falls directly on the mirror and the image of the source can be reflected back to the parallelizing lens. This method of lighting the microscope, so simple and generally applicable, has the one draw-back that the reflected image is rather faint and therefore not easily seen in a light room; at night or in a dark room it is very easily applied. If one is using the head- light lamp and the parallelizing lens is on the outside as shown in Fig. 14-15, one can tell easily when the image is reflected back into the lens from the bright image seemingly considerably nearer the 118 SIMON HENRY GAGE lamp filament than the blue image of the filament shown in the lens. To see these images one should look obliquely into the lens, that is, along a secondary not along the principal axis. One can also gain help in lighting by turning the mirror till a spot or ring of light appears on the upper end of the condenser. If the slide isin place with the oil for immersion, the spot of light will be bright. One must usually change the mirror slightly after the preparation is in focus to get the best light. CENTERING AND FOCUSING THE DARK-FIELD CONDENSER As can be seen by Fig. 6-7 the object must be in the focus of the dark-field condenser and this focus must be in the optic axis of the microscope. The dark-field condenser must have a special mounting with centering screws, which is the common method; or if the microscope has a centering sub-stage arrangement the dark-field condenser need not have a special centering arrangement, but be put in the centering substage fitting. Ordinarily there is no centering arrange- ment on a microscope and hence the dark-field condenser must have a special centering arrangement of its own. The whole is then placed in the usual bright-field substage condenser ring and raised until it is at the level of the top of the stage. Asa guide to centering, there is a circle scratched on the upper surface of the condenser (Fig. 7 c-r). With a low power (16 mm. objective or lower, and x5 ocular) one focuses down on the end of the condenser and if the small circle is not concentric with the circle of the field the centering screws are used with the two hands at the same time and adjusted until the circles are exactly even all around. Unfortunately this is not sufficient for the most satisfactory work, as it is rare that any two objectives will be exactly centered even though screwed into the same opening in the nose-piece, and much less likely to be centered if in different openings. To get the best results the objective to be used and the dark-field illuminator must be centered to each other. To accomplish this the following procedure has been found simple and certain: To start with the dark-field condenser is centered by the low objective as described above, and then with a crow-quill or other very fine pen one puts a very small point of Chinese white or other white ink in the middle of the little centering circle. This is MODERN DARK-FIELD MICROSCOPY 119 easily done if an objective of 20 to 40 mm. focus is used for centering the circle on the condenser. Now for centering the oil immersion or other high power objective the field of which is less than the centering circle, the objective is put in place, but no immersion liquid need be used for the centering. The top of the condenser has dusted upon it some starch or flour or other fine white powder so that in focusing down upon the top of the condenser there will be some shining particles to focus on if the white ink in the center of the circle should happen to be entirely out of the field, which is often the case. When the objective is in focus the centering screws are used to shift the condenser until the minute spot of white ink in the center of the circle is exactly in the middle of the field. In this way any objective may be centered with the condenser, and so far as the centering is concerned, one can be sure of getting the best results of which the condenser is capable. When the condenser is centered to the high objective, the starch particles and the white ink may be removed with a piece of moist lens paper or a soft cloth. Focusing the Condenser on the Object Level. This is one of the most essential steps for good dark-field work. If the objects are not in the focus of the condenser they will not be sufficiently lighted so that they can radiate enough light into the microscope to show all their details. One can proceed as follows, it being assumed that the preparation is mounted on a slide of the proper thickness for the given con- denser:—Use a low power, 16 to 50 mm. objective and light the microscope as described in the preceding section. Look into the microscope and focus on a saliva preparation. Move the slide around until there are plenty of epithelial cells in the field and then make slight changes in the mirror until the most brilliant light is obtained. With the screw device for raising and lowering the condenser shift the position up and down slightly until the smallest and most bril- liantly lighted point is found. When this is accomplished the condenser is in the optimum focus for that slide and will give the most brilliant light of which it is capable for the source of light used. Any preparation for examination can have the condenser focused upon it as just described. For experimental purposes a very satisfactory preparation for focusing the condenser is made as follows: A slide of the right thick- 120 SIMON HENRY GAGE ness is selected and cleaned and on one face near the middle is painted, with a fine brush, a very thin layer of Chinese white or other white ink. When this is dry, a drop of Canada balsam is put upon it and then a cover-glass. The white particles are very fine and serve admirably to show the focal point of the condenser. Such a slide can be kept as a standard and if the condenser is focused by its aid, it will be in the right position for any preparation mounted upon a slide of the same thickness as the standard. One must always remember, however, that many preparations have an appreciable thickness, and if the slide were of exactly the same thickness as the standard the light might be made more brilliant in a given case by focusing the condenser slightly upward for the higher levels of the preparation. This shows also that the slides selected for prepara- tions should be somewhat under the maximum thickness allowable for the given condenser. B Fig. 16. Face and sectional views of the focus of the hollow cone of light from dark-field condensers A—Sectional view of an optically perfect dark-field condenser in which the sun is represented as focused nearly to a point. No such condenser exists. B—Sectional view of a possible condenser focus. It is drawn out somewhat and spreads laterally. The variation in the thickness of slide which might properly be used is shown by the two parallel lines enclosing the elongated focus. C—Sectional view with a still more elongated focus. The parallel lines show that the variation in thickness of slide permissable is correspondingly increased. The apparent size of the sun’s image is shown on the axis above in each case. It is least sharp in C. The black line above the letters (A, B, C) represents the top of the condenser. Thickness of glass-slide to use. Mention has been made of glass slides of the proper thickness. What should this thickness be and how can it be determined are pertinent questions for one who is to get satisfactory results in dark-field work. The thickness of the slide with any given condenser is that which will bring the focus of the condenser—that is the image of the source of illumination—on the upper face of the glass slide where the object is located. Either MODERN DARK-FIELD MICROSCOPY 121 on the instrument or in the maker’s directions for its use the thickness of slide which should be used with it is given. If such definite infor- mation is not available or if a person wishes to determine for himself the proper thickness of slide to use, it may be found out as follows: An arc lamp and a dark room are necessary. The light should pref- erably be parallelized as shown in Fig. 13. The tube of the micro- scope is removed, and a piece of uranium glass with plane faces is placed on the stage and connected with the top of the condenser by homogeneous immersion liquid. The uranium glass is strongly fluorescent and shows with great definiteness the exact path of the beams of light from the condenser. One can see exactly where the light comes to a focus above the condenser and then the diverging beams above the condenser. If the condenser were perfect the rays would focus very accurately at a point above the condenser face, Fig. 16 A. This focal point is where the object should be placed and its distance above the condenser face gives the thickness of the slide to use. One can see that with an optically perfect condenser the thickness should be very exact to get the most brilliant image. [Ii the optical system is less perfect as shown in B Fig. 16 the rays do not all cross at one point, but over an appreciable thickness and anywhere within that elongated focus would give a brilliant illumination. In this case the thickness of the slide used could vary the length of this focus. In Fig. 16 C the focus is much elongated and the slide might vary greatly in thickness and still give a brilliant image. Above the sectional view of the focus in each case is given a face view of the brightest point as described above in getting the focus of the con- denser. One can readily see that the more perfect the focus at a point the smaller will be the point of light, and as all the rays are at that point it will be dazzlingly brilliant, while with B and C, where only part of the rays focus at any given level the circle of light will be less brilliant, but correspondingly greater in diameter. The larger circle of light has the advantage of giving a larger illuminated field, but the disadvantage of loss of brilliancy for the most exacting work. It should be mentioned also that as the focus gives an image of the source of light, the size of the source of light will also affect the size of the bright spot seen in looking down on the image. This is finely brought out by using the sun as a source and the arc light or the incandescent light. £22 SIMON HENRY GAGE One can see also from these figures that if the slide is too thin the objects will be partly in the dark space between the converging beams, and if the slide is too thick a part of the objects will be in the dark space between the diverging beams. If one sees the face view with a low power in either case there will be a ring of light and a central dark disc. and will look something like the central stop in Fig. 5 D As the preparations (blood, saliva, etc.) usually studied by the dark-field method have an appreciable thickness it is better to use a slide somewhat thinner than the optimum where the object is almost exactly at the level of the upper surface. If the slide is somewhat thinner the various levels of the preparation can be focused on by the condenser by slightly raising and lowering it as the case demands. For example, if the optimum thickness is 1 mm. it is better to use slides of 0.90 or 0.95 mm. and if the optimum thickness is 1.55 mm. it is better to use one of 1.50 mm. for ordinary preparations. Thickness of cover-glass and tube-length. These should be strictl in accordance with the construction of the objective. In all mode n objectives the makers state the tube-length and thickness of cover glass for which unadjustable objectives are corrected. As the dark- field illumination brings out very sharply any defects of correction in the objective, one should select a cover of the thickness, and the length of tube recommended by the maker of the objective. This applies particularly to dry, inadjustable objectives. If the objec- tives are dry and adjustable then corrections can be made for varia- tions from the standard of cover thickness or tube-length. If the objective being used is homogeneous immersion, the tube- length must be carefully attended to, but the thickness of the cover- glass is immaterial so long as it is thin enough to fall within the working distance of the objective; of course if it were thicker than that one would not be able to get the objective in focus (Bausch, ’90; Gage, ’87, 1912). PRACTICAL APPLICATION OF DARK-FIELD MICROSCOPY In the practical application of dark-field microscopy it is self- evident that it can be used successfully only with objects scattered, leaving a certain amount of blank or empty space between the objects. If the object being studied covered the whole field then it would all appear self-luminous and give a continuous bright appear- ance filling the whole field of the microscope. MODERN DARK-FIELD MICROSCOPY 123 In Biology, used in the comprehensive sense applied to it by Huxley, there come naturally the following groups of objects in which it is applicable, and likely to yield much information :— (A) Unicellular organisms in both the plant and the animal kingdoms. This of course would include the Protozoan Animals, the Bacteria, and other unicellular plants. (B) In the multicellular animals and plants it includes the natural fluid parts with their cellular and granular contents. In the verte- brates, including man, this would, for example, comprise the blood, and the lymph, with their cellular and granular contents; the tissue fluids, and the fluids in the natural cavities like the pericardial, the pleural and the peritoneal cavities, and the liquid found in the cavities of the central nervous system, the joint cavities and tendon sheaths. It is also of great service in the study of the liquids found in mucous containers, as milk, urine, bile, the saliva, the mucous in the nose, and other organs lined with mucous membrane. Furthermore it is of help in the study of isolated elements of the body like ciliated cells, etc. In a word it is applicable to the study of all animal and vegetable structures—including the pathologic ones—that are naturally isolated, or that can be artificially separated so that there is sufficient blank space between the structural parts. Dr. Chamot points out its help in the biological examination of water, in the study of foods, fibers, crystallization phenomena, sub- microscopic particles and colloids. He adds further (p. 40): ‘‘This method is invaluable for demonstrating the presence of very minute bodies or those whose index of refraction is so very nearly the same as that of the medium in which they occur as to cause them to escape detection when illuminated by transmitted light,” i.e., by bright- field microscopy. SUMMARY OF STEPS NECESSARY FOR SUCCESSFUL DARK-FIELD OBSERVATION 1. A powerful source of light must be available. 2. The dark-field condenser is put in place in the substage, and raised until the top is flush with the upper surface of the stage. The condenser is then accurately centered. If there is an iris diaphragm below the condenser it should be made wide open. 3. A homogeneous immersion objective with reducing diaphragm of about 0.80 N.A. is screwed into one of the openings of the nose- piece of the microscope. 124 SIMON HENRY GAGE 4. Slides and cover-glasses of the proper thickness are made very clean, and put in position for rapid handling. 5. The preparation to be examined—blood, saliva, etc.—is mounted on the slide and covered; the cover-glass is sealed with min- eral or castor oil, or with shellac cement. 6. The mounted preparation is held in the hand and one or more drops of homogeneous liquid put on the lower side of the slide oppo- site the cover-glass. The slide is then put upon the stage so that the homogeneous liquid makes immersion contact with the top of the condenser. The condenser may need to be raised or lowered slightly to make the contact perfect. 7. A drop of homogeneous liquid is put on the cover-glass. 8. The mirror is turned until there is a brilliant point of light in the homogeneous liquid on the cover. The objective is then lowered until it dips into the immersion liquid. 9. The microscope is then focused and the light made as brilliant as desired by turning the mirror. 10. Dark-field microscopy requires more accuracy of manipula- tion than does ordinary microscopy, but the increased visibility pays for all the trouble. A dimly lighted room is desirable for then the eyes are adjusted for twilight vision and can more easily make out the finest details. Method of Procedure. Asan example of the method to be followed in dark-field work, blood may be used. As pointed out nearly 50 years ago, by Dr. Edmunds, blood with dark-field illumination seems like a new structure, so many things are seen with the greatest dis- tinctness that are wholly invisible or only glimpsed when seen by the bright-field method. (1) Slides of the correct thickness for the condenser are selected and carefully cleaned. Cover-glasses are also cleaned and placed where they can be easily grasped. (2) For obtaining the fresh blood the part to be punctured should be cleaned well with 95% alcohol and then with a sterilized needle or Dr. Morre’s Haemospast, the puncture is made. The drop of blood exuding can be quickly touched by a cover-glass, and the cover put on the center of one of the prepared slides. If a small amount adheres to the cover, it will spread out in a very thin layer when placed on the slide. At least one preparation should be made which MODERN DARK-FIELD MICROSCOPY 125 appears quite red. In making the preparations one should work rapidly so that the various corpuscles will be in their normal numbers, and the fibrin will be formed only after the preparation is on the slide. If all the preparations are quite red, after a few minutes, one can be made thinner by pressing firmly on the cover by the ball of the thumb covered with gauze or lens paper. The gauze or paper absorbs the blood which runs out at the edge of the cover. In order to prevent evaporation and to help anchor the cover-glass so that it will not move by the pull of the viscid homogeneous immersion fluid, it is advisable to seal the cover by painting a ring of liquid vaseline (petroleum oil) or castor oil around the edge of the cover. One of the thick preparations should not be sealed, but kept for irrigation with normal salt to show especially the fibrin net-work. When ready to study the blood, put a large drop, or two large drops, of homogeneous liquid on the underside of the slide directly opposite the specimen, and place the slide on the stage of the microscope so that the immersion liquid will come over the face of the condenser. Then a drop of immersion liquid is put on the cover-glass and the objective run down into it. If the lighting is secured as explained above one soon learns to focus on the specimen. In general, the field all looks bright just before the objective gets down to the level for seeing the specimen. (a) The erythrocytes will appear like dark discs with bright rims owing to the convex borders. (b) The leucocytes appear as real white corpuscles owing to the granules within them which turn the light into the microscope. If the room is moderately warm—20 C or more—the leucocytes, some of them, will undergo the amoeboid movement, and the picture they present will be a revelation to those who never saw it or only with the bright-field microscope. From the clearness with which everything can be seen the minutest change can be followed, and also the most delicate pseudopod detected. Another striking feature will be noticed in the moving ones, that is, the vigorous Brownian movement of the granules in the part of the leucocyte with the amoeboid move- ment. In those showing no amoeboid movement there is usually no sign of the Brownian movement of the granules; also if a part of the leucocyte is not undergoing amoeboid movement the particles in it are usually motionless. 126 SIMON HENRY GAGE (c) The fibrin net-work will be seen like a delicate cob-web be- tween the corpuscles. In different parts of the specimen one can find all the appearances of the fibrin shown in text-books on the blood. (d) Chylomicrons appear everywhere like bright points in the empty spaces. They are in very active Brownian movement. These chylomicrons will probably be the most unusual part to those study- ing blood with the dark-field for the first time.* A very striking view of the fibrin net-work may be obtained by irrigating the thick blood preparation. If a drop of normal salt solution is placed on one edge of the cover-glass and a piece of blotting paper on the other the liquid is drawn through washing out many of the erythrocytes. If the washing out process is watched under the microscope the erythrocytes will be seen gliding over or through the fibrin net-work, or some of them will be anchored at one end and if the current is rapid the corpuscles will be pulled out into pear-shaped forms. The leucocytes look like big white boulders in the stream, wholly unmoved by the rushing torrent around them. HISTORY Almost always in human progress two steps must be taken (1) The discovery of the fundamental principles involved, and (2) the development of knowledge in other fields to make the application of the principles possible. Often a long time, sometimes a very long time, intervenes between the first steps and the final rendering of the knowledge a part of the common knowledge of mankind. The development of Dark-Field Microscopy is a good illustration of both the statements made. *The term chylomicron is from two Greek words; xbdés, juice or chyle, pxpév, any small thing, technically the one-thousandth of a millimeter (u). I have introduced this word to show the origin of these bodies from the chyle, and to indicate their general average size. Gulliver in 1840-1842, called these minute granules the molecular base of the chyle and showed that they were identical in the thoracic duct and in the blood vessels of the same animal. He gave their average size as 1/36,000 to 1/24,000 of aninch. They have been called by others free granules or granulations, elementary particles, etc. In 1896 H. F. Mueller described them as “A never-before observed constituent of the blood” and gave the name of haemoconia, literally, blood-dust. (See Gulliver, Lond. Edin. Phil. Mag. Jan. Feb. 1840; Appendix to Gerber’s Anatomy, 1842, and notes in the Works of Hewson, 1846; Mueller, Centralblatt f. allg. Path. u. path. Anatomie, Bd. 7, 1896, pp. 529-539). MODERN DARK-FIELD MICROSCOPY 127 The ancient opticians, thousands of years ago, knew well that the principle of contrast. was of the highest importance in rendering objects visible; but before this could be applied in microscopy, the microscope itself must be devised. This we see in its simplest form in the convex lenses of Roger Bacon (1266-1267) and in the now rarely used compound form of the Dutch spectacle makers, Jansen and Laprey (1590), composed of a convex objective and a concave ocular (Fig. 17). As a result of the Dutch Compound Microscope, Kepler was led to devise the modern form composed of a convex objective and a convex ocular (1610). But this Keplerian com- pound microscope has undergone many changes since its first concep- tion and many modifications to render it suitable for giving ability to show the delicate structures in nature with their true appearance. Among these changes may be mentioned the prepara- tion of achromatic lens combinations (Dolland 1757) for telescopes and applied to microscopic objectives between 1820-1830, put on the road to perfection by the introduction of the immersion principle (Hooke 1678, Brewster 1813, Amici 1840-1855) and by the aperture made available by the homogeneous immersion objectives of Tolles 1871-1874, and by the apochromatic objectives of Abbe. Condensers for lighting the object have also played a prominent part from that of Descarts (1637) to those recommended by Brewster (1831) and the homogeneous immersion condensers of Wenham, Tolles (1856 to 1871) and those now regularly made for homogeneous contact with the slide supporting the specimen. Among the subsidiary discoveries were necessary the arc-light of Davy (1800) and the right-angled arc lamp of Albert T. Thompson (1894) (Fig. 13) and the electric generators now everywhere available. In these last days also the gas filled or Mazda lamps with their close filaments of Tungsten which approximate in brilliancy and compactness of source to the arc lamp and greatly excel it in con- venience; and lastly of the production of a glass filter to give the light of the tungsten incandescent lamps true daylight quality, and make microscopic work by this artificial light as comfortable as the light from the northern sky (see Ives 1914, Gage 1915-1916). The time also between the first appreciation of the dark-field for the study of microscopic objects by Lister (1830), Reade (1838), Wenham (1850), Edmunds (1877), and the appreciation of the micro- scopical worker in general, came only after the invention of the ultra- 128 SIMON HENRY GAGE microscope (1903) and the application of the dark-field method to the study and detection of pathologic micro-organisms especially the Spirochaeta pallida (1905). It now promises to give much help in working out the activities and minute details of microscopic structure in animals and plants from the lowest to the highest. In the earliest stages of microscopic study the objects were seen by the light which they directed toward the microscope, and if over a dark background they appeared with varying degrees of brightness as if self-luminous; but even as early as 1637 (Fig. 17) Descartes microscope had provision for sending the light through the object. In this case much of the light did not reach the object at all, but passed on directly to the microscope. This mode of lighting showed the object more or less as a dark body on a brilliant background. Fig. 17. Descartes Dutch compound microscope with a parabolic reflector and a condensing lens (From Descartes Dioptrique, 1637). Ocular and Objective. The ocular is a plano-concave lens or amplifier, and the objective (N O P R) is a double convex lens. Reflector and Condenser. For objects to be lighted from above, there is a para- bolic mirror (c c); for those to be lighted from below there is a condensing lens (i i). MODERN DARK-FIELD MICROSCOPY 129 These two forms of lighting differed fundamentally in that with the first no light from the source passed into the microscope; but only that from the object, while with the second the light from the source as well as from the object got into the microscope. The significance of this fundamental difference for the aperture of the objective and for dark-field microscopy were first appreciated by Lister (1830), Wenham (1854), and Gordon (1906), and was practically applied in the manufacture of dark-field apparatus by Zeiss (1904) and Leitz (1905). In a word, it was the appreciation, as stated by Lister (1830) that-if the direct light from the source after it had reached the object, were prevented from entering the objective, by blacking the central part of the objective, then only the marginal part of the objective would be functional and that would receive only those rays from the object that were directed to it by the object itself, that is scattered light reflected, refracted, or diffracted, from the object, none of the light from the source getting directly into the microscope. As stated by Wright (p. 217) this is the method of dark-field microscopy by lighting the object with a solid cone of small aperture and, imaging it by hollow beams of large aperture. In practice this method has been discarded for the one by which the object is lighted by beams of light in such a direction with reference to the axis of the objective that none of them can enter the objective directly, and the light going to the microscope comes only from the objects themselves; they will therefore appear self-luminous on a dark background. The two conditions are (a) where the light is directed upon the object from above and, therefore away from the objective, and (b) where the light is directed upon the object from below, and therefore toward the objective (Fig. 3-4). If the light is directed upon the object from above and the object is over a non-reflecting background, the object will appear bright in a dark field. Of course, if it is on a light background that will also reflect light into the microscope and both object and background will appear light. It is assumed here that the object or objects cover only a part of the field, leaving plenty of empty space for background. In striving after a truly non-reflecting background three distin- guished men found the same thing, viz., that the only really black thing in nature is a black hole, that is, a space with black walls into which the light cannot enter directly. The dark walls absorb any 130 SIMON HENRY GAGE stray light, and the empty space gives no reflection. The first of these men devised for his microscopic purposes such a non-reflecting background by means of a small cup or well with the walls painted black. It is known as Lister’s black well (1826). The second dis- coverer was Chevreul (1839), who found in his work on Contrasts that a black space gave the only non-reflecting background. Sucha background was used by Marey for making moving pictures to show animal movements. Marey called it Chevreul’s black. The third was J. H. Comstock (1901) who found in the study and photography of spider webs that no pigment or fabric was black enough for a back- ground He therefore devised a deep box with the inner walls covered with black velvet and placed it so that the light could not shine into it. Over the mouth of this box the web was placed and lighted at right angles to the opening of the box. The feeble light the webs reflected served well for photography. These three men then absolutely independently found the same solution to their problem and doubtless many others have found also that Lister’s, Chevreul’s, and Comstock’s black space is the only really black thing in nature. From the time of Descartes (1637) the means for lighting objects from above the stage have been many. Some of them, like the bull’s eye condenser (Fig. 4, lens) and the side reflector send the light only from one side, while with the circular mirror of Descartes (Fig. 17) and the somewhat similar Lieberkuhn reflector (1740) the light is reflected from all sides upon the object. If now the object is on a dark background, it will appear as if self-luminous. From 1850 to the present two additional means have been devised for lighting from above. The first, following the suggestion of Riddell (1852) aims to make the objective its own condenser, the light being introduced into the side of the objective and reflected down by a small mirror or a prism (H. L. Smith 1865, Tolles 1866). (For a full discussion see W. A. Rogers, Journal of the Royal Micr. Soc., 1880, p. 754-758.) The other method referred to is that of Prof. Alexander Silverman of the University of Pittsburgh. It consists of a circular electric lamp and reflector which surrounds the objective and shines down upon the object. MODERN DARK-FIELD MICROSCOPY 131 Of course all objects lighted from above the stage will give true dark-field effects only when there is a black background, and the objects are scattered, leaving empty space between them. Dark-Field Microscopy with Substage Illumination. The first specific discussion of the possibility of dark-field microscopy with light from beneath the stage is found in a paper by the Rev. J. B. Reade of Cambridge University and is dated at Peckham, Nov. 1836, and is published as appendix No. 2 in the Micrographia of Goring and Pritchard, 1837. Reade says: p. 229: “To illustrate the two methods (Bright-field and dark-field) by reference to the telescope it may be observed that the discomfort of viewing spots on the sun not unaptly corresponds with the view of microscopic objects on an illuminated field; while the removal of all inconvenient and ineffective light from the field of the microscope corresponds with the clear and quiet view of stars on the dark blue vault of the firmament.” He brings out very clearly in his paper that no light from the source shall pass directly into the microscope, only that from the object, and that the object appears “sparkling with exquisite lustre on a jet- black ground.” The first appearance of this method in the general literature of microscopy which was found occurs in John Quekett’s Practical Treatise on the Use of the Microscope, Ist ed. 1848, pp. 178-179. He also furnishes a diagram to illustrate the method of lighting some- thing like fig. 4 of the present article, and remarks: ‘““The method consists in illuminating the object by a very powerful light, placed at such an angle with the axis of the microscope that none of the rays can enter it except those which fall directly upon the object, and are so far bent as to pass through it into the compound body,” i.e., into the tube of the microscope. It is referred to in the first edition of W. B. Carpenter’s “The Microscope and its Revelations” (1856) as follows: “Whenever the rays are directed (from below the stage) with such obliquity as not to be received into the object-glass at all, but are sufficiently retained by the object to render it (so to speak) self- luminous, we have what is known as the black ground illumination; to which the attention of microscopists generally was first drawn by the Rev. J. B. Reade in the year 1838 (1836-1837) although it had been practised sometime before not only by the author (Dr. Carpen- ter) but by several other observers.”’ 132 SIMON HENRY GAGE In addition to the condensing lens of Reade for throwing the very oblique beam of light upon the object, the mirror was used for low powers, and for higher powers, prisms were used especially by Nachet and Shadboldt (1850). It was seen however, that light from only one side might give rise to false appearances. In the third volume of the Transactions of the Microscopical Society of London, there appeared an epoch-making paper for dark-field microscopy. It is entitled ‘On the Illumination of Transparent Microscopic Objects on a New Principle.” It was read by its author, F. H. Wenham, April 17, 1850. After discussing the prisms of Nachet and pointing out the defect of oblique light from one side only giving rise to false images, he proceeds to show how the defect may be obviated by using two prisms giving light from oppo- site sides, or, and this is the epoch making part of the paper for dark- field work, by using a truncated parabolic reflector to give a circle of light. A dark stop was present to cut out all but the rays which exceed the aperture of the objective “‘So that the light which enters the microscope shall be that which radiates only from the object, as if it were seli-luminous.”’ The parabolic speculum was truncated so that the light would focus on an object mounted upon the ordinary glass slide. From this fundamental beginning, illumination by a hollow cone of light by the aid of the truncated parabola, all the advances in dark-ground illumination have proceeded. In 1851, Mr. Shadboldt says: “In order to obviate the objectional shadow (of lighting from one side only) as well as to procure a more brilliant illumination the parabolic condenser was projected by Mr. Wenham, to whom alone belongs the credit of having suggested the use of oblique illumi- nation in every azimuth, so as to produce a black field.” In this paper Mr. Shadboldt commends the use of a condenser made wholly of glass and depending upon internal reflections to take the place of the metallic parabolic mirror of Wenham. ‘This he named a sphero- annular condenser. In considering the obliquity required to have all of the light going to the object of an angle to fall outside the aperture of the objective, it seems to Shadboldt highly desirable that each objective to be used in dark-field work should have its own special condenser. That he understood as perfectly as we the possibility of using a single condenser for all objectives is shown by the following quotation, p. 157, “It is highly desirable that the MODERN DARK-FIELD MICROSCOPY 133 condenser should be constructed specially with reference to the aperture of the object-glass with which it is intended to operate; and for a reason to be given immediately, it will be seen that cutting off some of the rays, in order to make a condenser work with objec- tives of very much larger aperture, although quite practicable and even generally in use with the parabolic condenser, is not nearly so advantageous as the use of a separate condenser for every object- glass . . . of high power at least.” In 1856 Mr. Wenham himself advocates the use of a truncated paraboloid of solid glass with a central stop to cut out all the central rays which would not be internally reflected from the upper surface of the paraboloid. He brings out in the clearest manner possible the need of using immersion contact with the paraboloid to permit the very oblique rays to pass out of the paraboloid into the overlying substance. If the object is in water, then water immersion and when the object is mounted in balsam, he advocates the use of an immersion liquid between the glass slide and the paraboloid of cam- phine, turpentine or oil of cloves as their refractive index is nearly the same as crown glass and permits the passage of the rays of great aperture to pass on into the slide and the balsam containing the objects. We now use cedar oil or other homogeneous liquid for the same purpose. In 1877 Dr. James Edmunds presented before the Quekett Microscopical Club a paper on ‘‘A New Immersion Paraboloid Illuminator.” It consisted of a paraboloid of glass cut off at an exactly calculated distance below the focus, this distance varying in the four lenses which constituted his set, and the plane top being made optically continuous, and as nearly as possible optically homo- geneous with the substance of the slide, by means of a cementing fluid of high refractive index, such as anhydrous glycerine, castor oil, copaiba-balsam, oil of cloves, etc. The paraboloid lenses acted on the principle of total internal reflection, and each one was cal- culated for the thickness of the slide beneath which it was to be used (1/16th in 1/100 inch slides) so as to converge upon the object all of the light entering the base of the paraboloid. Parallel light should be thrown into the base of the paraboloid, and the most splendid effects were obtained. by means of direct sunlight. Water immersion objectives of 1/16th and 1/8th inch focus were used. After speaking of some test objects he says, p. 19: “With bacterial fluids, the effect 134 SIMON HENRY GAGE was equally remarkable. Saliva, blood, etc., viewed by a good dry quarter of about 95° (NA 74), were seen almost as new objects when lighted up by this paraboloid.” As it was recognized from the time of Reade that to gain the dark-field effect the light going to the object must be of an obliquity so great that it could not enter the microscope directly; this in- volved either a paraboloid or other dark-field illuminator of such great range that it might be used with all objectives, or the suggestion of Shadboldt must be followed that each objective have a paraboloid especially constructed to give it the best possible effect. This ques- tion naturally became very insistant when the water immersion objectives of large aperture came into use, and especially when the homogeneous immersion objectives came into common use (1880- 1890). It has finally been settled by adopting the first possibility, viz., the use of dark-field illuminators adapted for all objectives, the aperture of the objectives being reduced, where too great, to a point somewhat below 1.00 NA. This makes it possible to utilize a ring of light between 1.00 and 1.52 NA for the dark-field illumination, and this ring of light produced by the sun or the electric light has been found sufficient for practically all dark-field microscopy. It should be stated in passing that the ring of light produced by the dark-field illuminators usually falls between 1.00 NA, and 1.45 NA. Some fall below 1.00 NA and some only go to 1.30 or 1.35. The reducing diaphragms for homogeneous immersion objectives which have come to the writer with objectives have ranged from 0.40 NA to 0.80 NA. From 1907-1910 papers were written describing and figuring reflecting condensers made on the cardioid principle to take the place of the truncated paraboloid in dark-field work. The effort was made to so figure the component segments of glass that the spherical and chromatic errors would be largely eliminated, and that the entire ring of light could be brought to a more perfect focus than is possible with the truncated paraboloid: that is, to be optically more like A than like B or C in Fig. 16. A simple plate form for use on the top of the stage has also been devised. When this is used the substage condenser is turned out so that the light can pass directly up from the plane mirror to the condenser. This form is not easy to keep accurately centered. From the writer’s experience with quite a variety of these dark-field condensers in biological work MODERN DARK-FIELD MICROSCOPY 135 the paraboloids have proved the easiest to work with and the most generally satisfactory. As a final word,—now that the means have been found for fuller microscopic revelations, it behooves biologists to make the most of them; and in the study of the finest details in living things by this dark-field lighting, perhaps a truer conception of structure and action can be gained than by a too exclusive dependence on dead material treated with the endless variety of fixers and stains. Fig. 18. Chalet microscope lamp for bright-field microscopy (Two-fifteenths natural size). The lamp has two daylight-glass windows under the overhanging roof. The roof serves to shade the eyes. The source of light is a 100 watt Mazda C lamp bulb, the filament of which is centered with the windows. BIBLIOGRAPHY AKEHUuRST, S. C. 1914. Substage illumination by hollow cones. Jour. Quekett Micr. Club, Vol. XII, (1914) pp. 301-308. 3 pl. Bauscu, Edward 1890. The full utilization of the capacity of the microscope and means for obtaining the same. Proc. Amer. Soc. Microscopists, Vol. XII, 1890, pp. 43-49. Among other matters Mr. Bausch gives a very thoughtful discussion of the effect of the cover-glass and of tube length. BORELLUS, PETRUS 1655. De vero Telescopii inventore, cum brevi omnium conspiciliorum historia. Ubi de eorum confectione, ac usu, seu de effectibus agitur, novaque quaedam circa ca proponuntur. Accessit etiam centuria observationum microcospicarum. Authore Petro Borello, regis christianissimi con- ciliario, et medico ordinario. Hagae-Comitum, ex typographia Adriani Vlacq, MDCLYV (1655). 136 SIMON HENRY GAGE Evidence from those with personal knowledge that telescopes and micro- scopes were made by the Dutch spectacle makers, Zacharias Jansen, and Hans Laprey, 1590. CARPENTER, WILLIAM B. 1856. The Microscope and its Revelations. First edition 1856. An admirable statement of dark-field microscopy is given with the appara- tus devised up to that time for effecting it. Showing how greatly dark- field microscopy had been discarded in England one can compare the first and the 6th (1856-1881) editions of this work with the 8th edition, (1901). Cxamot, EmMire Monnin 1915. Elementary Chemical Microscopy. New York, 1915. This work is recommended not only for the account given of dark-field microscopy and its application, but for the ultra-microscope, the polari- scope, the micro-spectroscope and indeed all other chemico-physical apparatus used with the microscope, and their application in chemical and physical investigations. CHEVREUL, M. E. 1838. De la Loi du Contraste simultané des ‘Couleurs et de l’assortiment des objets colorés considéré d’apres cette loi. Paris, 1839. Work written 1835-1838. Third English edition, 1890. Part of Bohn’s Scientific Library. Comstock, J. H. 1912. The Spider Book. A manual for the study of spiders and their near relatives, the scorpions, pseudoscorpions, whip-scorpions, harvestmen, and other members of the class Arachnida, found in America north of Mexico; with analytical keys for their classification and popular accounts of their habits. New York. In this book are given pictures of the spider webs photographed against a black space, i.e., a deep box lined with black velvet. See p.181. The first photographs made in this way were taken in 1901. They were exhibited before the Entomological Society of America at its first meeting, Dec. 28, 1906. Conrapy, A. E. 1912. Resolution with dark-ground illumination. Jour. Quekett Micr. Club, Vol. 11, (1912) pp. 475-480. He says: “To get the utmost resolving power with dark-ground illumina- tion, the condenser must have not less than three times the NA of the objective. If the condenser has less than three times the aperture of the objective then the limit of resolution is found by taking 144 the sum of the apertures of objective and condenser: e.g., if cond. has NA of 1.40, and of obj. 1.00 NA, their sum is 2.40, 14 of 2.40=0.60 NA; ‘limit in this case.” Cox, Hon. Jacos D. 1884. Robert B. Tolles and the angular aperture question. Proc. Amer. Soc. Microscopists, Vol. VI, (1884) pp. 5-39. MODERN DARK-FIELD MICROSCOPY 137 This very able address, one of the ablest our society ever had the fortune to hear from its president, brings out with absolute clearness and fair- ness the steps in progress and the role played by Robert B. Tolles in actually making possible the final step, and taking that step, in his homogeneous immersion objectives. That is not all, he published the formula by which the objectives were made. The reading of this address is most strongly recommended to our younger members. Descartes (LAT. CARTESIUS), RENE 1637. Ocuvres, Publiées par C. Adam et P. Tannery sous les auspices du ministére de V’instruction publique, Vols. I-XII. Paris, 1902. The Dioptrique is in Vol. 6 of this edition, and the French and the figures are as in the original of 1637. In Cousin’s edition the figures are often considerably modified and the French modernized. Do.ionp, JoHN An account of some experiments concerning the different refrangibility of light. Read June 8, 1758. Philos. Trans. Roy Soc. Lond. 1758, pp. 733-743. This is the original paper on achromatic telescopes, etc. EDMUNDS, JAMES 1877. On a new immersion paraboloid illuminator. Jour. Quekett Micr. Club, Vol. V, (1877) pp. 17-21. Monthly Micr. Jour., Vol. XVIII, 1877, pp. 78-85. The Paraboloid was made optically continuous and as nearly as possible, optically homogeneous with the slide by the use of anhydrous glycerin, castor oil, copaiba-balsam or oil of cloves. He says that saliva, blood, and bacterial fluids gave remarkable effects, and were almost like new objects when seen with this paraboloid. GacE, S. H. 1917. The Microscope, an introduction to microscopic methods and to histology. 12th revised edition, Ithaca. 1917. GacE, S. H. and H. P. 1914. Optic Projection. Principles, installation and use of the magic lantern, the projection microscope, etc. Ithaca, 1914. GacE, S. H. 1887. I. Microscopical tube-length and the parts included in it by the various opticians of the world. II. The thickness of cover-glass for which unadjustable objectives are corrected. Proc. Amer. Soc. Microscopists, Vol. IX, 1887, pp. 168-172. This paper gave the information that has led to greater uniformity. GarpuKoy, N. 1910. Dunkelfeldbeleuchtung und Ultramikroskopie in der Biologie und in der Medizin. 5 plates, 81 pages. Jena, 1910. There is a bibliography of books and papers covering 9 pages (202 titles). Gorpon, J. W. 1907. The top-stop for developing latent power of the microscope. Jour. Roy. Micr. Soc., 1907, pp. 1-13. See also Wright, pp. 216-217. The plan is to cut out all of the central beam by a stop at the eye point instead of by opaqueing the central part of the objective. 138 SIMON HENRY GAGE GorRING AND PRITCHARD 1837. Micrographia, containing practical essays on reflecting, solar, oxy-hydro- gen gas microscopes, micrometers, eye-pieces, etc. 231 p. Many figures in the text, one plate. Whittaker & Co., Ave-Maria-Lane, London, England. 1837. Rev. J. B. Reade on dark-field, pp. 227-231. HALL, JOHN CHARLES 1856. On an easy method of viewing certain of the Diatomaceae. Quart. Jour. Micr. Sci., Vol. IV, (1856) pp. 205-208. In this paper Dr. Hall figures natural size, the “spotted lens” of that time, i.e., a very thick, more than hemisphere of glass with the central part opaqued. (See Quekett, 3d. ed., p. 135 where it is said that it is the invention of Thomas Ross.) Hall used this spot lens for oblique light with the ordinary bright field microscopy. He expresses astonishment that this instrument, designed to give dark-field effects, should give bright ones. He did not consider the fact that the aperture of this spot lens was insufficient to throw all the light outside of the aperture of the objective. One would get the same effect if a wide-angled homo- geneous immersion were used with a paraboloid, and no reducing dia- phragm were put into the objective. HEIMSTADT, OSKAR 1907. Neuerungen an Spiegelkondensoren (Aus der optischen Werkstatte von C. Reichert in Wien). Zeit wiss. Mikr., Bd. XXIV, (1907) pp. 233-242. HEIMSTADT, OSKAR 1908. Spiegelkondensor und Paraboloid. Zeit. wiss. Mikr., Bd. XXV, (1908) pp. 188-195. Erwiderung an Herrn O. Heimstidt, by Siedentopf, pp. 195-199. Dr. Heimstidt objects to some of Dr. Siedentopf’s statements in his paper, “Die Vorgeschichte der Spiegelkondensor.”’ Perhaps the spirit of the polemic will best be brought out by a quotation from Heimstadt, p. 188. “Vol allem beeintrachtigt es den Wert und auch die Neuheit dieser Dunkelfeldbeleuchtung nicht im geringsten, dass dabei langst ver- gessene Methoden ilterer englische Optiker wieder verwendt wurden.” In a word, it is well brought out in these papers where the fundamental ideas came from. IGNATOWSKY, W. V. 1908. Ein neuer Spiegel-kondensor. Zeit. wiss. Mikr., Bd. XXV, (1908) pp. 64-67 with figures of the substage and the plateform. See also Jentzsch, and Siedentopf. Jour. Roy. Micr. Soc., London, 1911, pp. 50-55. Jentzscu, Dr. FELIx 1911. The reflecting concentric condenser. Physikalische Zeitschrift, Bd. XI, pp. 993-1000. See also Ignatowsky and Siedentopf, Jour. Roy. Micro. Soc., 1911, pp. 50-55. KEPLER, JOHANNES 1604. Opera Omnia, Vol. II. Ad Vitellionem Paralipomena. (De modo visionis et humorum oculi usu.) 1604, pp. 226-229. 11 figs. Correct dioptrics of the eye here given, and also the explanation of the effect of convex and concave spectacles. MODERN DARK-FIELD MICROSCOPY 139 1611. Dioptrica.—Demonstratio eorum quae visui et visibilibus propter conspicilla non ita pridem inventa accidunt, pp. 519-567. 35 figs., 1611. The amplifier, real images, and erect images. The Keplerian microscope (Modern microscope.) LIsTER, JOSEPH JACKSON 1830. On some properties in achromatic object-glasses applicable to the improve- ment of the microscope. Philos. Trans. Royal Society London, Vol. 120 (1830) pp. 187-200. On p. 191 he discusses the effect of a ‘Stop behind the object-glass’’ (retro-objective stop) by which only the outer zone of the objective is used, the central zone being stopped out. See Wenham, 1854. Marey, ETIENNE JULES 1901. The history of Chronophotography. Annual Report of the Smithsonian Institution for 1901, pp. 317-340. On p. 320 Marey refers to Chevreul’s method of obtaining perfect black- ness. . MayALL, Joun, Jun. 1885. Cantor Lectures on the Microscope. Lectures delivered before the Royal Society of Arts, Nov. Dec. 1885. On pp. 95-96 are given the facts regarding the working out and production of homogeneous immersion objectives. Tolles is given due credit. Moorg, Dr. V. A. 1897. The Hemospast, a new and convenient instrument for drawing blood for microscopic examination. Trans. Amer. Micr. Soc., Vol. XIX (1897) pp. 186-188. After using this “spring needle lancet” individually and with large classes for many years I quite agree with Dr. Moore when he remarked to me the other day, “It is the most humane instrument I have ever seen for drawing blood.” I would like to add to this: And one of the most efficient. QUEKETT, JoHN 1848. A practical treatise on the use of the microscope including the different methods of preparing and examining animal, vegetable and mineral structures. First edition, 1848. Reade’s method given and illustrated pp. 178-179; Second edition, 1852, Reade’s method illustrated pp. 194-195. Third edition, 1855, Reade’s method, the method of Wenham, Spot-Lens method of Thomas Ross, the methods of Schadboldt and Nobert are all given. READE, REV. J. B. 1837. On a new method of illuminating microscopic objects, pp. 227-231 of Goring and Pritchard’s Micrographia, which see. (1837). Rocers, Ww. A. 1880. On Tolles’ interior illuminator for opaque objects. (With note by R. B. Tolles). Jour. Roy. Micr. Soc. London., Vol. IIT (1880) pp. 754-758. In this paper Rogers gives the history of the devices for making the objec- tive its own condenser by introducing light into its side and reflecting the light down upon the object. 140 SIMON HENRY GAGE SHADBOLT, GEORGE 1851. Observations upon oblique illumination; with a description of the author’s Sphaero-annular condenser. Trans. of the Micr. Soc. of London. Vol. III, pp. 132, 154. This paper was read in 1851. As this condenser is like the glass para- boloids now used for dark-field work, they are often called the Wen- ham-Shadbolt paraboloids. Shadboldt discusses prisms in this volume. SIEDENTOPF, H. 1907. Paraboloid-Kondensor, eine neue Methode fiir Dunkelfeldbeleuchtung zur Sichtbarmachung und zur Moment-Mikrophotographie lebender Bakterien, etc. Zeit. wiss. Mikr., Bd. XXIV, (1907) pp. 104-108. 1907. Die Vorgeschichte der Spiegelkondensoren. Zeit. wiss. Mikr., Vol. XXIV (1907) pp. 382-395. 16 figures are given of early forms. 1908. Mikroskopische Beobachtungen bein Dunkelfeldbeleuchtung. (Mitteil- ung aus der optischen Werkstitte von C. Zeiss, Jena) Zeit. wiss. Mikr. Bd. XXV (1908), pp. 273-282. Two plates of photomicrographs of the rays above the different condensers. See also under Heimstiadt. 1910. Cardioid-Condenser. Jour. Roy. Micr. Soc. Lond., 1910, pp. 515. See also Ignatowsky, and Jentzsch, Jour. Roy. Micr. Soc. Lond., 1911, pp. 50-55, where will be found a statement concerning the historical relation of these different condensers. STEPHENSON, J. W. 1879. A catoptric, immersion illuminator. Jour. Roy. Micr. Soc. Lond., Vol. II (1879) pp. 36-37. This condenser does not depend on internal reflection, but by a silvered surface around the central part. According to Siedentopf this is the condenser copied by Reichert; and according to Heimstidt Wenham’s truncated paraboloid was copied by Zeiss (See under Heimstadt). WeEnzHAM, F. H. 1850. On the illumination of transparent microscopic objects on a new principle. Trans. Micr. Soc. Lond., Vol. III. (1850) pp. 83-90. This is the paper by Wenham in which dark-field illumination is produced by a hollow silvered parabolic speculum. 1854. On the theory of the illumination of objects under the microscope with relation to the aperture of the object-glass, and properties of light; with practical methods for special differences of texture and colour. Quart. Jour. Micr. Sci. Vol. IL (1854) pp. 145-158. In this paper Wenham refers to the method of Lister (1830) for darkening the central zone of the objective so that no light can enter the outer zone, unless, as Wenham says, it is “radiated” from the object (See his fig. 1, and pp. 149-150 of the article). On p. 153, in the reference to the effect that his paper of 1850 had had in the microscopical world he says, “As proof of the utility and correctness of my theory, I have only to mention the many applications of it that have since that time (between 1850 and 1854) come into general use, in the way of adapting central stops to the achromaatic condenser, single (ie., “spot lenses”) and compound lenses, etc.” MODERN DARK-FIELD MICROSCOPY 141 1856. On a method of illuminating opaque objects under the highest powers of the microscope. Trans. Micr. Soc. Lond. in Quart. Jour. of Micr. Sci., Vol. IV, (1856) pp. 55-60. It is in this paper that Mr. Wenham insists on making homogeneous con- tact with the slide and the top of the paraboloid. It will be noticed that in this paper he speaks of Opaque Objects, while in the paper of 1850 he speaks of Transparent Objects. By reading the two papers it will be seen that many of the objects mentioned in the two papers are identical. This gains an explanation from the fact that he has ap- parently given up the notion that the objects were visible by their own “radiated” light, but by the light they reflect to the microscope. Consequently he represents (Fig. 4) the light from the condenser going to the cover-glass and being reflected from it down upon the object and he says that it makes the most perfect kind of a Lieberkuhn reflector. One can see instantly that when homogeneous immersion objectives are used there can be no total reflection from the cover. Woop, RoBert W. 1911. Physical Optics. New and Revised Edition, 1911. On p. 373, he discusses, ‘‘Penetration of the disturbance into the second medium,” and shows that going back to the time of Newton and Fresnel, it was known that while there was total reflection, the light seemed to pass for a minute distance into the rarer medium. This explains why one may get a brighter dark-field picture than is expected if objects are in optical contact with the slide. WRIGHT, Sir A. E. 1907. Principles of Microscopy, being a handbook to the microscope. London and New York, 1907. The writer has found this book the best and most thought-provoking of any that has been published on the microscope during the last 50 years. A NEW BLADDER FLUKE FROM THE FROG* BY Joun E. GUBERLET Bladder flukes have been reported a number of times from North American frogs but as yet very little work has been done on these forms in thiscountry. The European species, however, have received more attention and their complete life histories have been worked out. In North America the studies on frog bladder flukes have been carried on by only four authors, namely Leidy (1851), Bensley (1897), Stafford (1902, 1905), and Cort (1912). The localities from which these were reported are Toronto, Canada; Rice Lake, Ontario, Canada; Urbana, Illinois; Bemidji, Minnesota; and North Judson, Indiana. The writer has at hand another species of frog bladder fluke from Rana catesbiana taken at Stillwater, Oklahoma. In view of the fact that Cort (1912) has given a thorough review of the literature as well as a discussion of the nomenclature of this group, it is unnecessary to take up the history of the literature any farther at this time. The frog bladder distomes have been grouped into two genera by Loossand called Gorgodera (1899) and Gorgoderina (1902). The basis for this classification is on the number of testes which these animals have. The genus Gorgodera has nine testes while Gorgoderina has two. Of the latter genus there are known from North America three species, namely Gorgoderina simplex Looss, G. translucida Stafford and G. attenuata Stafford. Of the former genus there have been two species described, namely, Gorgodera amplicava Looss and G. minima Cort. The writer adds another species to the genus Gorgodera. GORGODERA CIRCAVA NOV. SP. In the summer of 1918 the writer found in the urinary bladder of a large bull frog (Rana catesbiana) twenty trematodes (Figs. 1 and 2) which belong to a new species of the genus Gorgodera. In the early part of the summer of 1919 another bull frog yielded two speci- mens of the same species of trematode. These forms were so firmly attached to the wall of the urinary bladder by means of the acetabu- *Contribution from the Parasitology Laboratory of the Oklahoma Agricultural Experiment Station, Stillwater, Oklahoma. 142 a A NEW BLADDER FLUKE FROM THE FROG 143 lum that it was necessary to tear the bladder apart in order to make the worms release their hold. The worms were killed by dashing hot corrosive acetic over them when they were well extended. In this way they were only very slightly contracted when killed. It was thought at first that this form belonged to the species Gorgodera amplicava Looss. Unfortunately, specimens of this species could not be obtained for comparison. From a study of the descriptions of G. amplicava in the literature on bladder flukes it was concluded that the species were not the same. The only other species of this genus known in North America is Gorgodera minima Cort. That species is much smaller than the one to be described here. The European forms are all much larger than any of the American species of Gorgodera. This species of distome is similar in activity and habit to the others of this genus. The anterior portion of the body is very active and moves about freely while the posterior region is less active but not sluggish. The cuticle of the anterior part of the body is marked with minute longitudinal striations. These markings extend to or slightly beyond the acetabulum. The part of the body which is anterior to the acetabulum is cylindrical but becomes flattened near the acetabulum while the posterior portion is somewhat flattened and rather opaque. The opacity extends from the posterior end forward to the region of the ovary. That portion of the body occu- pied by the ovary, vitellaria and acetabulum is fairly transparent. The length of the animal varies from 2.5 to 3.75 mm. with a width of .5 to .65 mm. in the region posterior to the ventral sucker. This form appears to be considerably smaller than Gorgodera ampli- cava which has a length of 3 to 5 mm., and larger than G. minima, that form being 1to2mm.inlength. The individuals which measure 2.5 mm. in length have large numbers of eggs in the uterus while in those of the larger size this organ is entirely filled throughout giving it the appearance of being a mere egg sac. In individuals which are less than 2.5 mm. in length no eggs are developed. The ventral sucker ranges from .60 to .75 mm. in diameter and is surrounded by a distinct circular sheath 0.05 to 0.135 mm. in width (Figs. 1 and 2, vss). This circular sheath around the acetabu- lum is very marked and is a rather distinct characteristic in this form. Therefore, I wish to propose the name Gorgodera circava for this species. 144 JOHN E. GUBERLET The sheath around the sucker forms a distinct space or cavity between the wall of the sucker and structures of the body (Fig. 7). Small muscle bands (Fig. 7, mb) bind the tissues of the body to the ventral edge of the sucker. There are also a few muscle bands and connective tissue fibers extending across the cavity which connect the sucker with the internal parts of the body. From the external appearance of a normal animal the sheath is only slightly apparent from a side view and appears only as a slight bulge around the sucker. In an animal with both ends curved ventrally the sheath forms a distinct fold around the acetabulum (Fig. 4). The ventral sucker with the circular sheath produces a structure from .65 to .8 mm. in diameter, which is somewhat broader than the greatest breadth posterior to the sucker. The oral sucker has a diameter ranging from .30 to .37 mm. with an average of .33 mm. for ten specimens. The ratio of the oral sucker to the ventral sucker ranges from 1.8:1 to 2.3:1 with an average for ten specimens of 2.1:1. As stated by Cort (1912:162) the acetabulum of G. amplicava is 2.5 to 3 times the size of the oral sucker. Therefore, G. circava is different in this respect. The mouth is situated in the oral sucker and appears as a tri- angular orifice in the posterior part of the sucker. The esophagus (Fig. 1, e) is a short narrow tube 0.14 mm. in length and 0.03 mm. in width. ‘The intestinal ceca (Fig. 1 and 2, i) are about 0.055 mm. in width and are dorsal extending from the esophagus to within a short distance of the posterior end of the body. They are widely separated to give room for the reproductive organs which lie between as well as ventral to them. ‘The ceca are dorsal and lateral to the testes. Some folds of the uterus pass to the lateral margins of the body and lie outside the ceca. The reproductive system of Gorgodera circava is similar to that of the other species of this genus. The principal differences lie in the relative size and shape of parts, such as the number of vitellaria, shape of ovary, seminal vesicle and ejaculatory duct. There are nine testes, five on the same side with the ovary and four on the other. They are irregular in shape and the anterior ones are some- what larger than those posterior. The shapes and sizes of the individual testes vary in different individuals but in general those which are anterior are proportionately broader than those posterior. With one exception the testes range about 0.23 mm. in length, 0.14 A NEW BLADDER FLUKE FROM THE FROG 145 to 0.17 mm. in breadth and 0.22 mm. in thickness. The testis which is most posterior is usually much smaller than the others, measuring about 0.17 mm. in length by 0.12 mm. in breadth and 0.21 mm. thickness. The testes on either side are connected by minute tubules. From the dorso-anterior edge of the anterior testis on each side arises the vasa efferentia (Fig. 5, ve). These tubules extend anteriorly and unite in the region of the vitellaria to form the vas deferens which passes forward to the vesicula seminalis (Fig. 3, ves). The vesicula seminalis is a large pyriform sac dorsal to the anterior edge of the ventral sucker. It has a length of 0.15 to 0.2 mm., breadth of 0.14 mm. and thickness of about 0.15 mm. The shape and size is somewhat modified according to the degree of expansion or contraction of the worm. The vesicula seminalis is entirely filled with sperm cells. From the dorso-anterior edge of the vesicula seminalis the ejaculatory duct (Fig. 3, ed) arises and curves ventrad for some distance and then extends forward to the common genital pore (Fig. 3,g). This duct has a total length of 0.16 mm. and in the proximal region has a diameter of 0.015 mm. Around the distal portion of the duct are grouped the prostate glands (Fig. 3, p), a group of unicellular gland cells. In this region the ejaculatory duct is much enlarged forming a large pouch (Fig. 3, ep), or lumen in the midst of the prostate gland. This pouch or enlargement of the duct is 0.07 mm. in length and 0.05 mm. in diameter. The ejacula- tory pouch as well as the duct is filled with sperms. The vitellaria (Fig. 2, v) are immediately posterior to the ventral sucker and anterior to the ovary. They are made up of two groups of six to eight follicles each. One group lies toward each side of the animal and they are connected by a transverse vitelline duct. This duct becomes enlarged to form the vitelline reservoir in the median line of the body (Fig. 6, vr). From the dorsal surface of the vitelline reservoir arises a small median vitelline duct (Fig. 5, vd) which passes dorsal into Mehlis’ gland where it unites with the ootype. The ovary is a distinct three-lobed structure 0.27 mm. in length, 0.24 mm. in breadth, and 0.21 mm. in thickness. This organ lies toward the ventral side of the body. It may occur on either the right or left side as about half of the specimens studied showed it on one side and the other half on the other. The oviduct arises from the dorsal surface of the ovary as a funnel-shaped structure with the broad part of the funnel attached to the ovary. It extends 146 JOHN E. GUBERLET dorsad for some distance as it becomes narrow and then curves laterally or anteriorly, after which it enlarges immediately into the fertilization space (Figs. 5 and 6, f). It then becomes narrow again and passes forward near the dorsal surface of the animal to Mehlis’ gland (Figs. 5 and 6, m) where it changes into the ootype. Mehlis’ gland is a small group of unicellular gland cells located between the posterior edges of the vitellaria and dorsal to the transverse vitelline duct. Laurer’s canal (Fig. 5 and 6, 1) passes from the proximal region of the oviduct between the fertilization space and the ootype and makes a slight lateral curve. It then goes anteriorly and dorsally to the point where it opens on the dorsal surface of the body either dorsal or lateral to the ovary. In passing from the ootype the uterus curves ventrad and bends back on itself (Fig. 5 and 6, u) in the median line of the body and goes posteriorly between the testes and finally reaches the posterior extremity of the body, where it fills with its numerous coils the region of the body posterior to the ovary and testes. The coils of the uterus become filled with eggs. Small masses of sperm cells are scattered throughout the coils of the uterus. The uterus finally emerges from the mass of coils in the region of the anterior testes (Fig. 2) and extends forward ventral to the ovary and vitellaria, passes dorsal to the ventral sucker and ventral, or slightly lateral to the vesicula seminalis to the genital pore (Fig. 3). The eggs of Gorgodera circava increase in size as they develop and pass from the ootype to the genital pore as in other species of the bladder flukes. In this case only the eggs in preserved specimens have been studied and no doubt there has been some shrinkage through the process of preservation. The eggs at the ootype measure about 0.016 mm. in length by 0.013 mm. in breadth; at the posterior end in the coils of the uterus 0.025 mm. in length by 0.019 mm. in breadth; while at or near the genital pore where they contain fully developed embryos, about 0.030 mm. in length by 0.023 mm. in breadth. The chief differences between the American species of Gorgodera lies in the size and shape of the animals; the structure, size and ratio in sizes of suckers; and the shape and relationship of the reproductive organs. Gorgedera minima, described by Cort (1912) is the smallest of the three species, it being 1 to 2 mm. in length and its acetabulum is 1.6 to 2 times the size of the oral sucker. Gorgodera amplicava A NEW BLADDER FLUKE FROM THE FROG 147 first described in this country by Bensley (1897), and reviewed by Stafford (1902), and again compared with Gorgodera minima by Cort (1912), is considerably larger being 3 to 5 mm. in length and its acetabulum is 2.5 to 3 times the size of the oral sucker. Gorgodera circava is 2.5 to 3.75 mm. in length and the acetabulum ranges from 1.8 to 2.3 times the size of the oral sucker. The acetabulum is also surrounded by a distinct circular sheath which is a distinctive char- acteristic of this species. In Gorgodera circava the vitellaria are composed of six to eight follicles in each group while Gorgodera amplicava has eight to ten in each and Gorgodera minima has nine to eleven. The ovary of Gorgodera circava is a distinct three-lobed structure while in G. minima it is only slightly lobed and in G. ampli- cava it has three to five irregular lobes with smaller or secondary lobes. The presence of the ejaculatory pouch in Gorgodera circava is another structure not found in either of the other species. The differences in the reproductive organs and the presence of the circular sheath around the acetabulum clearly sets Gorgodera circava off from the other species. LITERATURE CITED BENSLEY, R. R. 1897. Two forms of Distomum cygnoides. Centr. f. Bakt., u. Infekt., 21:326-331. Cort, W. W. 1912. North American frog bladder flukes. Trans. Amer. Mic. Soc., 31:151-166. Lery, J. 185i. Contributions to Helminthology. Proc. Acad. Nat. Sci. Phila., 5:205-209. Looss, A. 1899. Weitere Beitrige zur Kenntniss der Trematoden-fauna Aegyptens. Zool. Jahrb., Syst., 12:521-784. 1902. Ueber neue und bekannte Trematoden aus Seeschildkréten. Zool. Jahrb., Syst., 16:411-794. STAFFORD, J. 1902. The American Representatives of Distomum cygnoides. Zool. Jahrb., Syst., 17:411-424. 1905. Trematodes from Canadian vertebrates. Zool. Anz., 28:681-694. EXPLANATION OF PLATE XIII All drawings made with the aid of camera lucida. Fig. 1. Dorsal view of Gorgodera circava, X35. Fig. 2. Ventral view of Gorgodera circava, X35. Fig. 3. Reconstruction from sagittal sections showing ends of reproductive organs and genital pore, X130. Fig. 4. Outline drawing of small specimen which is bent ventrally at both ends causing the acetabular sheath to form fold around sucker, X35. 148 JOHN E. GUBERLET Fig. 5. Reconstruction of female genital organs from sagittal sections, X120. Fig. 6. Reconstruction of female genital organs from frontal sections as seen from dorsal view, X120. Fig. 7. Sagittal section through ventral sucker to show ventral sucker sheath, X35. e esophagus ed ejaculatory duct ep ejaculatory pouch ex excretory pore f fertilization space g genital pore 7 intestinal ceca 1 Laurer’s canal m Meblis’ gland b muscle bands 0 ovary os oral sucker ov zs. Abbreviations oviduct prostate gland uterus vitellaria vas deferens vasa efferentia vesicula seminalis median vitelline duct vitelline reservoir ventral sucker ventral sucker sheath testes )Yyt TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XX XIX = ke yp = : ods GUBERLET PLATE XIII ’ : p ‘ ’ . ri .. . é id ‘ ; r é \ 3 \| . i ; ) ‘ . $ ‘ « ‘ d ‘ 4 i , o 1 ‘ : : 7 , . 4 . 5 ’ 4 c " 1 , ‘ . ' . . ¥ 4 ‘ ‘ : 4 ; , i . 4s : J 1 , , f ‘ : F . ; ‘ im ‘ ye inet J 7 q ' : : . i, Y : 3 an ; ‘ ; od / rs . \ . . . LABELING ILLUSTRATIONS BY Z. P. METCALF North Carolina State College and Experiment Station Sometimes really good illustrations are spoiled by faulty or poorly made labels and not infrequently biological illustrators do not do sufficient labeling to make their illustrations clear. The thought is frequently expressed by good draughtsmen that labeling is difficult and is therefore to be avoided, or they say they wish that they had been born with the ability to letter drawings properly thus expressing clearly that in their own opinions their drawings are not labeled as they should be. With these thoughts in mind it seems not amiss to outline the following methods that may be used for labeling biological illustrations. It frequently becomes necessary to indicate separate parts on an illustration, hence it becomes necessary to label the drawing. This may be done in a variety of ways. If the person making the illustra- tion has enough ability he may make the lettering free handed. Another method is to select letters or figures from printed matter. These may then be cut out and pasted on the illustration in the proper place. Still another method is to buy the cut-out letters and figures and paste these on the illustration. The sets desired may be written on the typewriter and cut out and pasted on the illustration. Labels may be printed directly on the illustration. And lastly guide lines may be drawn to the margins of the illustrations where they may be connected with type set up in the ordinary way when the illustration is printed. Regardless of the method of labeling selected care should be exercised to make the labels as neatly and accurately as possible. Care should also be exercised to see that the lettering is sufficiently large to stand the necessary reduction if the illustration is reduced. The labels of biological illustrations are generally indicated in the following manner: (1) by Arabic numerals, (2) by the initial letters of the name of the parts of the object labeled, (3) by abbrevia- tion of the names of the parts of the object labeled, (4) by a sequence of letters, and (5) by the full names of the parts of the object. In the first four methods it is necessary to print an explanation of the 149 150 Z. P. METCALF labels. The fifth method requires no explanation. The method selected will depend upon the personal choice of the draughtsman. There is much to be said in favor of the fifth method provided there are not too many parts to label or the names are not too complicated. By this method the attention is not distracted by having to search through a long list of explanations. If it is preferred to abbreviate the names, then there is much to be said in favor of the second and third methods, for the initial letters and the abbreviation will indicate the real name of the part. If either of these methods is selected the explanations should be arranged alphabetically, so that it will not be necessary to look through the entire list to find the explanation for any abbreviation. The labels may be placed at the margin of the illustration or directly on the illustration. The method we select will depend to a great extent on the nature of the illustration. If the parts are large enough so that the labels may be placed directly on the part without obscuring any details this is perhaps the best method. For many illustrations, however, this is not possible. The labels should then be placed at the margin. This latter method necessitates the use of guide lines. Guide lines may be simple straight lines or they may be brackets. Brackets are used to indicate areas of considerable extent which could not be indicated by a single line. Instead of the bracket, two lines drawn at an angle to each other may be used. The straight lines may be solid, dotted or dashed lines. If a dashed or dotted line is used care should be taken to get the dots of uniform size or the dashes of uniform length. As a general proposition guide lines should be straight and should run parallel to the main margin of the drawing if possible. On very light drawings the guide lines should be black. If the guide lines run over alternate dark and light areas it is advisable to use a double line, one part being black and the other part white. Care should be exercised to keep guide lines of uniform thickness. This may readily be accomplished by using a ruling pen. Ordinary liquid India ink may be used for black lines and any good grade of Chinese white for white lines. Care should be taken not to make the lines so thick that they will look unsightly when the drawing is complete. On the other hand, the lines should not be so delicate that they will not stand the necessary reductions. LABELING ILLUSTRATIONS 151 Cut out letters or figures which are gummed on the back may be purchased in a wide variety of styles and sizes. These are very desirable for labeling drawings especially if the correct size and a suitable style are selected. Care should be taken to see that the separate letters are pasted in a straight line. This may readily be accomplished by drawing a faint pencil line to indicate the bottom of the letters, and then bringing the letters to this line. Cut out letters have the advantage that they may be pasted directly on the illustration, and will obscure only a minimum amount of detail. Labels may be written on the typewriter using a good black record ribbon. In making labels on the typewriter only a new ribbon should be used and the type should be thoroughly clean so that good sharp impressions can be secured. These labels may then be cut out and pasted on the drawing as recommended above for printed labels. The chief difficulty with this method is that the labels are too small unless the illustration is not to be much reduced in repro- duction. Type written labels may be enlarged by making a negative from them by any of the enlarging methods, and then printing a positive from this negative on a smooth gaslight paper. This method is advocated chiefly where we need a large number of labels of the same kind. Labels may be selected from printed matter and pasted on the drawing. It is necessary to bear in mind the amount of reductions that will take place in reproducing the drawing. The ordinary book type is about 9 points, therefore if the drawing is reduced to one third the original labels should be 28 point. If the drawing is reduced to one fourth the original label will have to be 36 point. It is usually difficult to find letters of sufficient variety in these sizes. Special labels may be set up by the printer but this is usually a very expensive method. Plate XIV shows the various sizes of printed letters and may be used to determine the size of letters that it is necessary to use. Thus if the drawing is reduced to one third labels the size of 36 point will appear as 12 point or 18 point will appear as 6 point, etc. The various sized letters on this plate may be traced on thin tracing paper in India ink and pasted on the drawing. HAND PRINTED LABELS FROM RUBBER TYPE Labels may also be printed by hand from rubber type directly on the illustrations. For printing labels from rubber type we will 152 Z. P. METCALF need a set of rubber type of the proper size, holder to hold the type, and a stamp pad filled with faint blue ink. The proper combinations of letters are set up in the-holder, bearing in mind that the type are inverted and reversed. The type in the holder are then stamped in the pad and then on the drawing. The labels are then traced over with India ink. It is necessary to trace over labels made with a rubber stamp because the margins are not clear cut. The advantage of using the pale blue ink is that if the illustration is reproduced by ordinary photographic processes the blue will not show and need cause no trouble if slight errors are made. Rubber type may be secured in a variety of styles and sizes. A neat legible style should be selected and a size selected so that it will stand the necessary reduction. Sets of complete alphabets may be purchased or separate stamps may be produced from dealers in office supplies. The former has the advantage that any label may be readily set up. The latter is preferable if many labels of the same kind are to be printed at one time. The holders for rubber type are usually supplied with the sets of type. These holders are convenient and since they are adapted to the size type with which they are supplied they leave little to be desired. Stamp pads for this purpose should be inked with a faint blue ink as this color is not very active, photographically it does not bother the engraver. After the labels have been stamped with the faint blue ink they must be finished up with black India ink. This requires a fine pen and a little attention to details, but can be done with considerable rapidity after a little practice. HAND PRINTED LABELS FROM METAL TYPE Labels may also be printed from the regular metal type of the printer very much as the rubber type is used. To print labels from metal type we will need some black printers ink, a font of type of proper size, a holder for the type and a compositor’s roll. The ink used for hand printed labels of the metal type is the regular black printers ink. This usually requires thinning to work properly. Benzine, gasoline or xylol may be used for thinning the ink. For this purpose the ink is placed on a piece of glass and the solvent is added drop by drop while the ink is worked with a spatula, until it is of the proper consistency. Experience soon teaches when the ink is of the proper consistency. When it is thought that the ink is properly mixed a small amount of the prepared ink is spread on the LABELING ILLUSTRATIONS 153 compositor’s roll and the type in the holder is stamped on the roll and printed on a piece of paper. If the ink is in the proper condition and has been properly spread on the roll enough will adhere to the face of the type to make a good label. If the ink is too thin it will spread when we attempt to printa label. If it is too thick not enough of it will adhere to the face of the type to print a good label. Fig. 1. Type holder for printing labels. b, bur of the stove bolt which is soldered q, quads which are used to fill out the to the type box. line of type h, heads of stove bolts used to clamp the _ 5, stove bolt used to clamp the type in movable plate against the type the line m, movable plate t, type The type holder (Fig. 1) used for hand printed labels is a shallow box made of brass. The height of the box is a little less than the height of the type. One side of the box is movable and is fastened to the opposite side by means of four set screws. This is used to lock the type in rows. One end of the box has a set screw which is used to lock the type. This holder is used very much as an ordinary rubber stamp is used. If only one figure or letter is to be printed in each label it is not necessary to use the type holder, but the individ- ual types can be held in the hand very readily. Type is set up in an inverted and reversed position. Each piece of type has little grooves called the nicks which indicate when the type is in a proper position. As soon as a line of type is set up a glance will reveal whether all of the characters are in the proper position. The characters to be used are picked out from the type box one at a time and placed in the holder which is held in the left hand in an inclined position so that the type will lay against the fixed side of the holder. As soon as the label is completely set up the rows of type are locked in place by tightening the set screws 154 Zz. P. METCALF which fasten the movable side and the end. At first the set screws are only set tight enough to hold the type firmly in place. A soft wooden block is then placed on the face of the type and the type is leveled up by pounding with a light hammer. The properly set up label is firmly pressed on to the inked compositor’s roll and the inked type is then stamped on the illustration. Care being taken to press the type down firmly at all points without allowing it to move. The advantages of hand printed labels are that they are very neat and accurate and that they may be made by any one without previous experience. The chief disadvantage is that it is somewhat laborious to set up the type. But with the large sized type used in printing labels for illustrations this is not a very large item. It must be remembered that it requires several hours for the printers ink to dry and care must be exercised in handling the illustrations or the labels may be ruined. FREE-HAND LETTERING Occasionally it is not possible to letter an illustration by any of the methods given above, in that case it is necessary to have recourse to free-hand lettering. Free-hand lettering is a special kind of free- hand drawing by means of which the draughtsman learns to draw the design of letters neatly and rapidly. There are no special tricks of the trade about lettering that cannot be learned by the biologist who will conscientiously try to master the subject. The first consideration in free-hand lettering as in other kinds of free-hand drawing is to get the main proportions. After the main proportions are secured the details are added. The more important details are added first then the finer and finer details until the letter- ing is complete. Just as the individual letters are found to vary one from the other so in printing a line of lettering it will be found neces- sary to space the letters carefully with reference to each other, other- wise the lettering will not have a neat appearance when finished. In lettering each letter is influenced by the letters on each side of it so that no general rule can be laid down which will make it possible to always place a letter the proper distance from its neighbors. The only rule that can be given is that all letters should seem to have the same amount of space allotted to them. Obviously this amount of space will vary with the different letters and with the letters on each side of it. Thus a capital I requires less space than a capital M. LABELING ILLUSTRATIONS 155 Then, too, a capital I will require more space if placed between a capital M and a capital N than if placed between a capital E and a capital T because these letters have a great amount of free space whereas the M and N have practically no free space. The letters in each word must be studied, therefore, in order to determine the proper spacing. Trials should be made in order to see just what spacing looks the best. If this is done critically gradually a proper conception of proper spacing of letters will be acquired. The usual error made by beginners is to space the letters too far apart. Letters look better when they are crowded well together. The letters in any design that is to be treated in free-hand letter- ing should be sketched in with a pencil complete before finishing up any of the letters. This is done in order to insure a proper balance of the words with each other and a proper spacing of the letters. In sketching letters it is usually advisable to draw two faint lines one for the top and the other for the bottom of the letters. Sometimes it is advisable to divide this space by a third line so that certain letters may be carefully drawn with rapidity. After the base lines are drawn the letters are sketched in spacing each letter with refer- ence to the other letters, and indicating at first only the general outlines of the letters. Corrections should be made until the whole has a well balanced appearance. Some letters may then be carried forward and the principal minor details indicated, making any necessary corrections in the other letters in the line to maintain the balance. After experience has been gained letters may be sketched in ink free-hand, especially such forms as the Gothic. And any one having considerable lettering to do should practice this form of letter- ing, but the art of lettering is soon lost unless it is used day by day. After the pencil sketch of a line of lettering is finished the letters may be finished with India ink on drawings or with black water color or oil color on paintings. In doing this the borders of the main letters are finished first and then the borders of the finer details; the body of the letters being filled in last of all. Care must be taken in finishing up the borders not to exceed the limits penciled and to keep all straight lines straight and all curved lines a true curve. In filling in the body of the letter care must be taken not to allow the color to run over the borders that have been finished. In finishing large letters a ruling pen and a straight edge may be used for the longer 156 Z. P. METCALF straight lines on the borders of the letters but on the smaller letters and for all fine details a pen must be used free hand. The idea is prevalent that the forms of letters are fixed but nothing is farther from the truth. There are certain broad general styles of letters such as the Roman and Gothic but the variations in these styles are as many as there are draughtsmen. A few of the more important styles are discussed below and plates showing stan- dard letters are given, not with the idea that these should be copied slavishly but that these designs may be helpful in producing letters for drawing and may serve to indicate the main styles. All letters occur in two forms, capitals usually called caps and small letters called lower case. If there are only a few letters in a group as in the abbreviated signs used to label parts of a drawing either caps or lower case or both kinds of letters may be used, but if there is a series of words it is better to use lower case letter throughout as we are used to reading words printed in lower case types. Words in lettering should be well separated so that there is no doubt as to the limits of the separate words. ‘The rule is that the words should be separated at least by a space equal to that occupied by the widest letter and slightly mere space would be better. The Gothic letter is the simplest letter because it is formed of lines of a uniform thickness throughout. Gothic letters exist in two forms, a vertical Gothic and an inclined Gothic. In the vertical Gothic alphabet the main axis of the letters is vertical and since the lines are all of a uniform thickness it is a fairly easy alphabet to letter in a free-hand manner. For convenience of discussion the letters are divided into the following groups, (1) letters composed of straight horizontal and vertical lines, (2) letters composed of horizon- tal or vertical lines with diagonal lines, (3) letters composed of straight and curved lines and (4) letters composed of curved lines only. Furthermore it is convenient to define a full bodied letter as a letter occupying as much horizontal as vertical space. For pur- poses of analysis the letters are drawn on cross section paper each letter occupying a vertical distance of five units. The thickness of the stroke is only 2/3 of a unit. In the first group of letters we have the capitals E, F, H, I, L and T and the lower case letters i, ]. In the capital E it will be noted that the letter is not a full-bodied letter as the foot occupies only 41¢ units and the cap only 4 units. The tongue of the letter occupies LABELING ILLUSTRATIONS 157 only 21% units and is placed only slightly higher than the middle. The capital F is identical with the E except that the foot is omitted. Care should be taken not to extend the cap too much or the letter will look top-heavy. ‘The capital H occupies about 4 units as other- wise it looks too broad. The tongue is placed on a level with the tongue in the E and F, that is slightly above the middle. The capital I needs no comments as it is simply a straight line with a thickness of 2/3 of a unit. The foot of the capital L is about 31% units in length to prolong it makes it appear unwieldy. The full bodied lower case letter occupies only three-fourths the space allotted to the full bodied capitals and the width of stroke is only a half unit. The small lower case letters occupy only two-thirds of the vertical space occupied by the large lower case letters. Therefore the body of a small lower case letter like i would occupy only one-half of the vertical space allotted to a capital letter, hence 244 units the dot being placed one full unit above the top of the letter. The lower case 1 would occupy 34 of the vertical space allotted to a capital. To the second group belong the capitals A, K, M, N, V, W, X, Y and Z, and the lower case letters k, v, w, x, y and z. The capital A occupies the full width of five spaces below and slopes to the top line uniformly on both legs. The top does not end in a sharp point but in a point that is about one-half unit wide. The tongue of the A is placed about one and one-half units above the base line. The capital K is somewhat difficult as it is composed of two diagonal lines at different angles. The top diagonal is usually placed about three and one-half spaces from the vertical stroke and at such an angle that if it were projected the lower border of the diagonal would strike the base line one full unit to the left of the vertical stroke. The lower diagonal is placed four units from the vertical stroke and at such an angle that its top border projected would strike the top of the vertical stroke. The capital V is simply the capital A inverted and the tongue omitted. The capital M is simply the V with two vertical strokes added on each side. Note that these vertical strokes end in their full width and not reduced as in the case of the top of the A and the bottom of the V. The capital N consists of two vertical strokes four units apart connected by a diagonal running from the top of the left hand stroke to the bottom of the right hand stroke not the reverse as is frequently seen in lettered signs. The diagonal is placed at such an angle that the vertical strokes will end in full 158 Z. P. METCALF width on both the base and top limiting lines. The capital W may be considered as two V’s contracted to occupy only four spaces each and united so that the apex of the jointed diagonals shall occupy only half a unit each. The capital X is simply two diagonals which cross each other in the center. This letter is therefore a full bodied letter. The capital Y is composed of two arms which are six units apart and run at such an angle as to unite two and one-half units from the base line. The foot of the capital Z is four and one-half units long and the cap only four units long. The cap and the foot are con- nected by a diagonal placed at the proper angle. In the lower case letters the stem of the K occupies the full vertical unit for lower case letters and the diagonals of the letter bear the same relation to each other that they do in the capital K but they are reduced to one-half. The lower case v, w, x and z are the same as the caps except they are reduced to one-half. The lower case y is the same as the lower case v with the right diagonal extended below the base line, the full length allotted to lower case letters. In the third group we have the capitals B, D, J, P, R and U; and the lower case letters a, b, d, e, f, g, h, m, n, p, q, r, t, and u. The capital B may be considered as a capital E with the ends of the cap and the foot connected to the tongue by arcs of circles. It will be noted that this makes the top part of the letter somewhat smaller than the bottom. The capital R may be considered as a capital F with the cap and tongue connected as in the B and a tail added to the lower part. The tail of the R should extend beyond the top part of the letter at least a full unit otherwise the letter will look top-heavy. The P is similar to the R without a tail but the top part of the P is made longer by dropping the tongue about one-half unit below its position in R. A capital D is produced by using a foot and cap similar to the foot and cap in the capital B and connecting these two horizontal lines by a regular curve. ‘The capital J and U are similar to each other save that the J has a single vertical arm and the Ua double arm. The J is somewhat narrower occupying only three and one-half units whereas the U occupies about four and one-half units. The vertical arms are in each case about three and one-half units long. In the lower case letters b, d, p and g all have the same form and the q is simply the g with the stem turned to the left to distinguish these two forms; and the a is quite similar but with a shorter stem. The lower case u may be taken as the type of another LABELING ILLUSTRATIONS 2 nef 59 group of letters. It is essentially like the capital U with the right arm extended to the base. The lower case n is simply the u turned upside down and reversed and the m is simply two ns contracted slightly and united. While the lower case h is simply the n with the left side prolonged the full length of lower case letters. ‘The lower case f, j, r and t are essentially vertical lines with short curved tails added. The capitals O and Q are essentially complete circles which extend slightly above the top line and slightly below the base line. The capitals C and G are parts of circles and offer no special difficulties. The capital S is composed of two curves joined by a third curve and is one of the most difficult letters to handle. The upper and lower limbs are arcs of ellipses whose major axes lie in horizontal planes with the major axis of the upper ellipse slightly shorter than the major axis of the lower ellipse and with their minor axes about in the ratio of two to three. The lower case 0, a and s are essentially the same as the corresponding capitals and lower case c is similar with a horizontal line across the upper two-thirds of the circle. The Gothic numerals may be taken as standard just as we took the Gothic letters. It will be noted that the numerals 1 and 4 are the only ones composed of straight lines only. The numeral 1 is a straight line 144 unit wide, the numeral 4 has a total width of four units and is drawn so that the horizontal tongue is one and one-half units above the base line. The numerals 3 and 8 are essentially the same being composed of two broad ellipses joined together the upper ellipse having a shorter major axis than the lower ellipse. The minor axes of the two ellipses bear a relation of about 2 to 3 to each other. The numeral 0 is merely a flattened ellipse with a major axis of 5 units and a minor axis of 4 units. The numerals 6 and 9 are the same being simply placed in different positions. It will be noted that they are essentially the same as the numeral 0 except for the forma- tion of the small ellipse at the bottom of the 6 and the top of the 9. Note further that the tail of the 9 is somewhat expanded being near the base line and that the tail of the 6 is somewhat contracted being near the top line. This preserves the proper balance. The numeral 5 is essentially the same as the 6 except that the tail is composed of a straight vertical and horizontal line. The top is somewhat contracted to preserve the proper balance. The numeral 7 is four units wide with the curved vertical stroke ending on the base line about one unit to the right of the point where the horizontal line starts on the 160 Z. P. METCALF top limiting line. The numeral 2 is the most difficult in the whole series as it consists of acompound curve. ‘The top curve is somewhat like the top curve of 3 but is flatter and the bottom curve is more pronounced than the curve in the numeral 7. The inclined Gothic is the vertical Gothic inclined at about 15° from the perpendicular. We need not make any special analysis of the separate letters as that has been done for the vertical Gothic. This is a favorite alphabet for draughtsmen who do a great deal of lettering as it can be done with great speed and if carefully done it looks neat and is very legible. For these reasons it is especially valuable for large amounts of labeling. The Roman Gothic is in many respects a more pleasing alphabet than the Gothic. The basis of the letters is the same as for the Gothic but certain lines called body strokes are shaded by being made thicker, while some lines are made thinner than in the Gothic letter. The shaded or body strokes are usually made one unit wide and the hair lines are usually made one-half unit wide. Roman Gothic letters of widely different appearances may readily be secured by varying the width of the hair line. It should be noted that the curved body strokes are slightly thicker than the straight body strokes. Where curved lines join straight lines the union is made very gradually so that the eye cannot detect the point of union. The Roman letter is a further modification of the Roman-Gothic by the addition of serifs to the strokes so that no lines end with a line of uniform thickness. This is the type of letter used in most printing and is the most difficult letter for the draughtsman to handle. How- ever, it is perhaps the neatest appearing letter and should be used more extensively than it is at the present time. The separate letters need not be analyzed separately because they have essentially the same form as in the Gothic alphabet. The body stroke is usually considered as one unit in width for the straight lines and slightly wider for the curved lines. Sometimes variation in this standard is made for some special purpose. The hair lines vary greatly in different styles of this letter from lines as thin as they can be drawn easily to lines at least half a unit in width. By varying the widths of the hair lines, letters of quite different appearances may easily be secured. ‘The serifs demand special attention and must be drawn neatly and accurately or they will ruin the appearance of the lettering. Horizontal serifs are usually about one unit in length and are con- LABELING ILLUSTRATIONS 161 nected to the main stroke by a gentle curve which is made tangent to the main stroke and to the serif. Vertical serifs are usually made about one and one-half units long and are connected to the main stroke by a gentle curve which is tangent to the serif but not tangent to the main stroke. Exception, however, must be made in the case of the double serifs found on the tongue of the E and F, which are smaller than the other vertical serifs. In letters like E, s and Z in which are two vertical serifs the upper one is made slightly shorter than the lower one for the sake of appearance. In the capital J and some of the lower case letters it will be noted that curved lines instead of ending in straight serifs end in curved comma shaped marks called kerns. Instead of filling in the body strokes of Roman letters solidly they may be indicated by two hair lines. This makes a neat appearing letter and is useful for display titles but is difficult to execute and therefore seldom employed in labeling biological illustrations. 162 Plate XIV. Plate XV. Plate XVI. Plate XVII. Z. P. METCALF EXPLANATION OF PLATES Letters and figures of various sized type. Vertical Gothic letters analyzed. Roman Gothic letters analyzed. Roman letters analyzed. TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XXXIX 30 point —————_________ ABCDEFGHIJK abcdefs hijk 1234567890 24 point ABCDEFGHIJKLMNO abcdef¢ hijkImno 1234567890 IS point ABCDEFGHIJKLMNOPO abcdefghijklmnopq 1234567890 12 point ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz) 1234567890 S point ABCDEFGHIJKLMNOPQRSTUVWXYZ} abcdefghijklImnopqrstuywxyz 1234567890 O point eR Ae LEE ee fghijklmnopqrstuy 1234567890 NL PLATE XIV METCALF “twee vy me TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. X XX1IX METCALF BEALE, XV f . certs oe oe gers ] Lf ~ a) ; ; a a (> Sean ite: Sekt: 5 h ; CF i - ad : : . : : ; R | 7 J wee rhe te ney, <- - ~ : a fi ; x= ; ‘ " fo en a | | Tea re bees ae 4 ; z : are ; , - - ft ' ' TRANSACTIONS OF THE AMERICAN MICROSCOPICAL S¢ CIETY VOL. XXXIX PLATE XVI fe fests Hoots Pah Sa eae et — iL al , ‘ : ” - rs - TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XXXIX METCALF XVII [eA LyANA RL ab TEE cued DEPARTMENT OF NOTES AND REVIEWS It is the purpose, in this department, to present from time to time brief original notes, both of methods of work and of results, by members of the Society. All mem- bers are invited to submit such items. In addition to these there will be given a few brief abstracts of recent work of more general interest to students and teachers. There will be no attempt to make these abstracts exhaustive. They will illustrate progress without attempting to define it, and will thus give to the teacher current illustrations, and to the isolated student suggestions of suitable fields of investigation. —[Editor.] ENTOMOLOGICAL ABSTRACTS Position of Micropterygidae —Tillyard (1919, Proc. Linn. Soc. N. S. Wales, 44:95-136) has made an extensive study of the remark- able family of archaic moths, the Micropterygidae. Chapman (1917) removed the genus Micropteryx from the remainder of the family and proposed a new order, Zeugloptera, for its reception. Comstock (1918), on the other hand, removed the whole family Micropterygidae from the Lepidoptera and placed it as a new suborder of the Trichop- tera. Tillyard finds no justification for either of these views. The proposed “‘Zeugloptera”’ is found to lack a single character not found in some other order. In all of the Micropterygidae M, does not occur as a separate vein of the forewing; the characteristic trichopterous wing-spot is lacking; the pupal wing-tracheation is complete; the scales are broad and possess numerous striae; and functional frenula are present. These characters definitely rule out the possibility of these insects being Trichoptera, and necessitate the conclusion that that they must be archaic Lepidoptera. Micro pterygidae.—Braun (1919, Ann. Ent. Soc. Am., 12:349-367) has also attacked the problem of the position of the Micropterygidae. A study of wing structure in the primitive Lepidoptera shows, accord- ing to this writer, that while the Micropterygidae stand close to the common ancestor of Lepidoptera and Trichoptera they are true Lepidoptera and have given rise to all of the remainder of that order by several divergent lines, one represented by the Nepticulidae, another by the Hepialidae, and a third ‘‘much branched line includes the frenate Lepidoptera, of which some members such as the Prodoxi- dae, Incurvariidae, etc., conserve some of the trichopterous characters of their ancestry and must therefore be regarded as the most primitive of the Frenatae.”’ 163 164 PAUL S. WELCH Filariasis in U. S.—F¥rancis (1919, U. S. Publ. Health Service, Hygienic Lab. Bull. No. 117) reports on a study of filariasis in Southern United States. Filaria bancrofti is the species concerned and one endemic focus has been located in this country at Charleston, S. C. Of 400 individuals examined in that city, 77 were infected with microfilaria, whereas of 1,470 examinations in nine southern cities outside of Charleston only 9 showed infection. The data indicated that cases outside of Charleston have derived the infection either from residence in Charleston or from residence at some place outside of the United States, as in Cuba. Transmission occurs only through the mosquito, but the certainty of the process is limited by the follow- ing facts: (1) No multiplication of the filaria in the mosquito; (2) The small number actually passing successfully through the mosquito; and the still smaller number which reach the lymph glands of man; (3) Male and female filaria must find lodgment in the same lymph gland of man in order that reproduction occur; (4) Infection of mosquitoes can occur only during a few hours before and after midnight; (5) The biting act of the mosquito only drops the micro- filaria on the free surface of the skin of man whence it must penetrate the intact skin. The mosquito, Culex fatigans, was found to be the transmitter. The anatomy of the mosquito proboscis in relation to filaria transmission is discussed and the inward and outward courses of the filariae pointed out. The former is through the stilette bundle along with the ingested blood, while the latter is through the interior of the labium. Eight well executed plates, mostly in color, add to the value of the paper. Polyembryony and Sex.—Patterson (1919, Journ. Heredity, 10:344-352) reports results of a study of the origin and development of mixed broods in polyembryonic Hymenoptera and the ratio in production of males and females. In 162 broods of Copidosoma gelechiae, 90 were female, 62 male and 10 mixed. The sex ratio was found to be approximately 3 females to 2 males. The great excess of females in four of the mixed broods suggested the possibility that both sexes might arise from a single fertilized egg. In Paracopidoso- mopsis floridanus, 1.7% of the broods were pure female, 11.3% pure male, and 87% mixed. The percentage of males varied from 0.06 to 72.07 and in over 58% of the broods less than 10% of the indivi- duals in any brood were males. In Platygaster rubi not a single pure male brood was found. This, however, might be explained by the NOTES AND REVIEWS 165 prevailing conditions which make it unusual that an unfertilized female might escape. Only 6 of the 105 broods were pure female. In the 99 mixed broods, the number of females, in every brood, exceeded the number of males. In 53 broods only one male per brood appeared, 17 had 2 males each, and 13 had 3 each. The other broods showed a varying number, but not exceeding 10. That some mixed broods result from two parasitic eggs, one from a fertilized female and one from a virgin female, seems very probable but two diffiulties stand in the way of the exclusive application of this application, namely, (1) simultaneous emergence of individuals of a mixed brood, and (2) striking predominance of females over the males in the great majority of broods. A Paracopidosomopsis female, in about 66% of the cases, deposits two eggs in the host egg at a single oviposi- tion, and in the majority of cases both eggs were found to be fertilized. A host egg mass of 28 eggs exposed to a mixed brood of parasites yielded 14 with 1 parasitic egg, 11 with 2 each, and 3 with 3 each. Eight of the 11 indicated two ovipositions, while 3 seemed to represent one oviposition. In each of the 3 remaining eggs the three parasitic eggs apparently represented different ovipositions. Therefore the two-egg explanation seems inadequate for the mixed broods of Platygaster. It is proposed that some of the mixed broods may result by one fertilized egg giving rise to both sexes through abnormal behavior of the two sex chromosomes during early cleavage, as for example, somatic non-disjunction in which certain blastomeres receiving but one x chromosome would produce male embryos. Origin and Significance of Metamorphosis——Crampton (1919, Bull. Brooklyn Ent. Soc., 14:33-40; 93-101) considers critically the problems. of origin and significance of metamorphosis in insects. Presence or absence of metamorphosis, although worthy of careful consideration, cannot be regarded as an important factor in determin- ing the relationships of insects, according to this writer. An ancestral group, it is contended, may include some forms which have ‘‘devel- oped the tendency towards a metamorphosis, to a marked degree, while other representatives of the same ancestral group do not exhibit any marked indications of such.a tendency.” Plecoptera, Embiidae, Dermaptera, Coleoptera and their allies constitute the ‘“plecopteroid superorder” and are regarded as the ancestral group from which the higher insects were derived. This group contains forms exhibiting well marked metamorphosis and some which do not. The higher 166 PAUL S. WELCH forms are divided into two super orders: (1) the “‘psocoid superorder”’ containing the Psocodae, Mallophaga, Anopleura (Pediculidae, s.b.), Hemiptera, Homoptera and their allies—a group in which few mem- bers exhibit traces of metamorphosis; and (2) the “neuropteroid superorder’’ comprising the Neuroptera, Hymenoptera, Mecoptera, Diptora, Siphonaptera, Trichoptera, Lepidoptera and their allies, all being predominantly holometabolous. Thus it is suggested that we might expect the coleopterous representatives of the ancestral group to be somewhat nearer the derived holometabolous group, while the remaining representatives of the ancestral group would be nearer the derived non-metabolous group. To account for the origin of meta- morphosis among some of the ancestral forms, it is thought that there arose a tendency (by mutation, etc.) of the immature stages to differ from the adults, resulting eventually in stages which could enter an environment untenable by the adult. Such forms, favored by natural selection, would tend to persist and thus there would appear a “propensity towards the production of complete metamorphosis.” Against the claim of Handlirsch that cold produced metamorphosis, Crampton argues that “insects in which the tendency toward meta- morphosis was already well developed, were better equipped than their less fortunate fellows, to penetrate the less favorable regions of winter-frost, etc., and there establish themselves.’”? No support is found in embryology or palaeontology for the view that larval stages represent “free-living embryos.” Disagreement with any view that environment causes metamorphosis is expressed. The pupal stage is regarded as the ‘‘making over”’ period necessitated when immature and adult stages come to differ so markedly that a great change must be involved in the transition. Larvae stages are regarded by this author as having some phylogenetic significance and may yield valuable hints as to relationships. Whether primitive types of larvae represent ancestral conditions more nearly than adults do seems uncertain. In some cases it seems to be true but in other instances the larvae have become far more specialized than the adult, thus involving secondary characters. PauL S. WELCH Department of Zoology, University of Michigan TABLE OF CONTENTS For VoLuUME XXXIX, Number 3, July, 1920 Protozoa of the Devil’s Lake Complex, with two plates, by C. H. Edmondson.... 167 Age, Growth, and Scale Characters of the Mullets, Mugil cephalus and Mugil curema, with seven figures and seven plates, by A. P. Jacot................ 199 TRANSACTIONS OF American Microscopical Society (Published in Quarterly Instalments) Vol. XXXTX JULY, 1920 No. 3 PROTOZOA OF THE DEVIL’S LAKE COMPLEX, NORTH DAKOTA BY CHARLES HowaArp Epwuonpson, PH.D. University of Oregon! CONTENTS PAGE RLU CLONMEL eC ree ers era Maina e Auvinen io ueiee al onion kt arate RR 167 1h, BSH VANO)OTINY C3 dela at Dec A Nn ee Al ar Ue en a ae ER Sl 171 MPORIEIPRDIC TEES et AGis tokio FAM ees Ryde), eA shee ct olaire egies Sata 190 PRENCMEEAT, allay CONCLUSIONS Aiea sy-sepaie Sohne UE erate el heel eh bua anss ee 193 Si. LMG Vena She bats a bscark Miah te AUERC Oey ree LAC SER EORTC EGA RU MC en Tee EIT Re ey 195 1. INTRODUCTION Several reports previously issued? have described the physio- graphic and chemical characteristics of Devil’s Lake situated in Ramsey County, North Dakota. Ina recent paper Dr. R. T. Young,’ of the University of North Dakota, has indicated something of the possibilities and limitations of the lake from a biological point of view, as well as the general scope of the work already accomplished in that direction. It will only be necessary, therefore, to set forth a few of the specific features of this water area which may have some bearing on the report to follow. ! The investigations included in this report were carried on at the State Biological Station of North Dakota. ? Biennial Report of the State Biological Station of North Dakota, 1911-12. Pope, T. E. B. Devil’s Lake, North Dakota, a study of physical and biological conditions, with a view to the acclimatization of fish. U.S. Bureau of Fisheries Docu- ment 634, 1908. Simpson, H. E. The Physiography of the Devil’s-Stump Lake Region, North Dakota. Sixth Biennial Report of the State Geological Survey of North Dakota, 1912. Upham, W. The Glacial Lake Agassiz, Mon. 25, U. S. Geological Survey, 1895. 3 Young, R. T. The Work of the North Dakota Biological Station at Devil’s Lake. The Scientific Monthly, December, 1917. 170 CHARLES HOWARD EDMONDSON, PH.D. Biological studies of Devil’s Lake made by the United States Bureau of Fisheries in 1908 indicate the presence of four vertebrate inhabitants of the lake, namely: a stickleback, Eucalia inconstans; a minnow, Pimephales promelas; the hellbender, Crytobranchus alleghaniensis; and the leopard frog, Rana pipens. Among the metazoan invertebrates reported are crustaceans, rotifers, nematodes, a flat worm, an arachnid and a number of species of insects. One may collect the shells of at least fifteen molluscs from the water line on the shore, but no living forms have been taken from the lake. Sponges, coelenterates, polyzoans and annelids are apparently en- tirely absent. Investigations of the protozoan fauna of the Devil’s Lake complex were undertaken as a part of the general biological survey of that water area. Although, in many respects, this fauna was found to be such as one might expect in a fresh water lake of similar depth, yet some very pronounced differences were disclosed. The almost total absence of shell-bearing rhizopods may possibly find its explanation in the chemical analysis of the water. Arcella vulgaris Ehrenberg, a very constant and usually abundant form in fresh water, was rarely observed and two species of Difflugia, which are among the most com- mon protozoa in lakes where there is considerable ooze, were taken only in situations where the salinity of the water must have been materially reduced by the in-seepage of surface water. A species of Euglypha was taken in the overflow of the lake water from the fish tank. The only other shelled rhizopod observed was a single speci- men of Cyhoderia ampulla Leidy, taken from the main lake. The fact that the ooze at the bottom of the lake at times has been found to be entirely free from oxygen might also be a contributing fac- tor to the scarcity of these usually common bottom-dwelling rhizopods of the shell-bearing type, although the presence of the larvae of a cer- tain midge in this ooze as well as the work of Birge and Juday in Wisconsin,’ where a considerable number of animals were found at the bottom of lakes in the absence of oxygen, would hardly seem to make this factor one of great importance. Experiments of a preliminary character, recorded at the end of the taxonomic part of this report, indicate that certain protozoa having 7 Birge and Juday, The Inland Waters of Wisconsin; Wisconsin Geological and Natural History Survey, 1911. PROTOZOA OF THE DEVIL’S LAKE COMPLEX den adjusted themselves to fresh water conditions are not, in all cases at least, readily adaptable to the waters of Devil’s Lake. The writer wishes to acknowledge his indebtedness to Dr. R. T. Young, Director of the State Biological Station of North Dakota, whose co-operation made this report possible, and to Mr. E. G. Moberg for his valuable assistance in collecting material. 2. TAXONOMY SUBPHYLUM SARCODINA CLASS RHIZOPODA SUBCLASS AMOEBAE ORDER GYMMAMOEBIDA Famity AMOEBIDAE Genus Amoeba Ehrenberg, 1831 Amoeba proteus (Résel). Der kleine Proteus Résel, Insecten Belustigung, 1755, tab. 101. Amoeba proteus Leidy, Pr. Ac. Nat. Sc., 1878. Occurrence.—Associated with Ruppia in Whipple Bay, Creel Bay, Minnewaukon Bay, Six-mile Bay, East Lake, and also taken from the east side of the main lake and from the overflow of lake water from the fish tank near the laboratory. Amoeba radiosa Ehrenberg. Amoeba radiosa Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence.—Rarely observed. Taken with Ruppia from Minne- waukon Bay, also from Big Mission Lake. Amoeba limax Dujardin. Amoeba limax Dujardin, Histoire Naturelle des Zoophytes In- fusoires, Paris, 1841. Occurrence.—Associated with Ruppia and algae at the head of Creel Bay, Big Mission Lake (numerous), Little Mission Lake (numerous), and the east side of the main lake (numerous). Amoeba verrucosa Ehrenberg. Amoeba verrucosa Ehrenberg, Die Infusionsthierchen als Volkom- mene Organismen, 1838. Occurrence.—Observed but once, from material taken along the east side of Creel Bay. 172 CHARLES HOWARD EDMONDSON, PH.D. Amoeba guttula Dujardin. Amoeba guttula Dujardin, Histoire Naturelle des Zoophytes Infusoires, Paris, 1841. Occurrence.—Taken from algae near Brannon’s Island, from both ooze and floating algae in Creel Bay, from the east side of the main lake, and from sediment on rocks near the Station. Amoeba striata Pénard. Amoeba striata Pénard, Etudes sur les Rhizopodes d’eau douce. Mem. Soc. Phys. et Hist. Nat. Geneve, 1890. Occurrence.—One specimen only observed in plant infusion from Stump Lake. Amoeba vitraea (Hertwig and Lesser). Dactylosphaerium vitraem Hertwig and Lesser, Ueber Rhizopoden und denselben nahestehende Organismen. Arch. Mikr. Anat. Vol. 10, Suppl., 1874. Occurrence.—Taken from the east side of Creel Bay. ORDER TESTACEA FAMILY ARCELLIDAE Genus Difflugia Leclerc, 1815 Difflugia pyriformis Perty. Difflugia pyriformis Perty, Zur Kenntniss kleinster Lebensformen in der Schweiz, 1852. Occurrence.—Only observed from Big Mission Lake in a location where fresh water seeps into the lake. Difflugia constricta Ehrenberg. Difflugia constricta Ehrenberg, Abh. Akad. Wiss. Berlin, 1841. Occurrence.—Taken from Big Mission Lake in the same situation as the preceding species, and also from the head of Creel Bay near the entrance of a sewer. Genus Arcella Ehrenberg, 1830 Arcella vulgaris Ehrenberg. Arcella vulgaris Ehrenberg, Abh. Akad. Wiss. Berlin, 1830. Occurrence.—Taken in ooze from the head of Creel Bay and from near the station, also from Big Mission Lake near the in-seepage of fresh water; abundant in the latter locality. PROTOZOA OF THE DEVIL’S LAKE COMPLEX ilif/s) FAMILY EUGLYPHIDAE Genus Cyphoderia Schlumberger, 1845 Cyphoderia ampulla (Ehrenberg). Diffiugia ampulla Ehrenberg, Bericht Preuss. Akad. Wiss., 1840. Occurrence.—One specimen only has been observed. Taken from Whipple Bay among Ruppia. Genus Euglypha Dujardin, 1841 Euglypha alveolata Dujardin. Euglypha alveolata Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Taken from the overflow of lake water from the fish-tank near the Station. Observed but once. SUBCLASS HELIOZOA ORDER APHROTHORACIDA Genus Actinophrys Ehrenberg, 1830 Actinophrys sol Ehrenberg. Actinophrys sol Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence.—Rarely observed, taken from among Ruppia in Minnewaukon Bay. SUBPHYLUM MASTIGOPHORA CLASS ZOOMASTIGOPHORA SUBCLASS LISSOFLAGELLATA ORDER MONADIDA FaMILy RHIZOMASTIGIDAE Genus Cercomonas Dujardin, 1841 Cercomonas sp. Figures 1-3, Plate XVIII. Probably Cercomonas longicauda Dujardin. Very plastic with caudal filament often developed. Diameter, when spherical, 10u Occurrence.—Observed in infusions from Stump Lake only. Famity HeTEROMONADIDAE Genus Monas Miiller, 1786 Monas sp. Figures 4, 5, Plate XVIII. Very plastic. Diameter, when spherical, 20u. May represent Monas fluida Dujardin. Occurrence.—In the ooze from Creel Bay. 174 CHARLES HOWARD EDMONDSON, PH.D. Monas sp. Figure 8, Plate XVIII. Length 9; body persistent in form, anterior region very granular. Corresponds in some degree to Monas irregularis Perty. Occurrence.—In the ooze from Creel Bay. From a stale culture of Ruppia, Creel Bay. Monas sp. Figure 7, Plate XVIII. Body moderately plastic. Length, when extended, 15-18y. Possibly same as figures 4 and 5. Occurrence.—In the ooze from Creel Bay. ORDER HETEROMASTIGIDA FAMILY HETEROMITIDAE Genus Heteromita Dujardin, 1841 Heteromita globosa (Stein). Bodo globosus Stein, Der Organismus des Infusionthiere, Abth. 3, 1878. Occurrence.—In dredged material from Creel Bay. Heteromita sp. Figure 6, Plate XVIII. But little of detail determined. Length 54. The form probably represents Heteromita ovata Dujardin. Occurrence.—Taken from ooze on rocks near the Station. ORDER POLYMASTIGIDA FamMILy POLYMASTIGIDAE Genus Trepomonas Dujardin, 1841 Trepomonas agilis Dujardin. Trepomonas agilis Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Taken from Big Mission Lake, Whipple Bay, from the ooze of the main lake and from the east side of the main lake. Abundant in the latter locality. ORDER EUGLENIDA FamiILty EUGLENIDAE Genus Euglena Ehrenberg, 1830 Euglena viridis Ehrenberg. Euglena viridis Ehrenberg Abh. Akad. Wiss., Berlin, 1830. PROTOZOA OF THE DEVIL’S LAKE COMPLEX WAS Occurrence.—Observed from Minnewaukon Bay, Big Mission Lake, in the ooze from Creel Bay and from the east side of the main lake. Euglena desus Ehrenberg. Euglena desus Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence.—Minnewaukon Bay, Six-mile Bay, near Brannon’s Island, Big Mission Lake, Little Mission Lake, East Lake, and the ooze from the main lake. Genus Phacus Dujardin, 1841 Phacus pyrum (Ehrenberg). Euglena pyrum Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence.— Minnewaukon Bay, Creel Bay, Big Mission Lake (numerous), and the east side of the main lake. Genus Eutreptia Perty, 1852 Eutreptia viridis Perty. Eutreptia viridis Perty, Zur Kenntniss kleinster Lebensformen in der Schweiz, 1852. Occurrence.—From the surface among Ruppia, Big Mission Lake. Famity ASTASIIDAE Genus Astasia Ehrenberg, 1830 Astasia tricophora (Ehrenberg). Trachelius tricophorus Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence.—Among Ruppia from Whipple Bay, from Creel Bay, in the ooze from Big Mission Lake, and among algae near Brannon’s Island. FAMILY PERANEMIIDAE Genus Petalomonas Stein, 1859 Petalomonas mediocanellata Stein. Petalomonas mediocanellata Stein, Der Organismus der Infusions- thiere, 1878. Occurrence.—Taken from the surface of Big Mission Lake and from the ooze of the main lake. 176 CHARLES HOWARD EDMONDSON, PH.D. Petalomonas sp. Figure 10, Plate XVIII. Has some resemblance to Petalomonas ervilia Stein. Conspicuous groove entire length of the body. Length 36un. Occurrence.—From the ooze of Creel Bay. Genus Heteronema Dujardin, 1841 Heteronema acus (Ehrenberg). Astasia acus Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence.—From Six-mile Bay and from the ooze of Creel Bay. Genus Anisonema Dujardin, 1841 Anisonema grande (acinus) (Ehrenberg). Bodo grandis Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Anisonema acinus Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Among Ruppia and algae at the head of Creel Bay. Genus Notosolenus Stokes, 1884 Notosolenus sp. Figure 9, Plate XVIII. Length about 15y. Occurrence.—From Whipple Bay, Stump Lake and from the overflow of the fish-tank near the Station. ORDER CHLOROFLAGELLIDA FAMILY TETRAMITIDAE Genus Tetraselmis Stein, 1878 Tetraselmis cordiformis (Carter). Cryptoglena cordiformis Carter, Annals of Natural History 1858. Occurrence.—Taken from Stump Lake only. FAMILY POLYTOMIDAE Genus Polytoma Ehrenberg, 1838 Polytoma uvella Ehrenberg. Polytoma uvella Ehrenberg, Die Infusionsthierchen als Volkom- mene Organismen, 1838. Occurrence.—Found at the head and along the east side of Creel Bay. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 177 FAMILY TRIMASTIGIDAE Undetermined genus Undetermined species. Figures 11, 12, Plate XVIII. Description.—Body elongate, somewhat compressed, slightly plastic, attenuated posteriorly; surface marked longitudinally by several conspicuous ridges; flagella three in number arising from the anterior extremity, equal and equalling the body in length; nucleus and contractile vacuole unobserved. Length 20u. Occurrence.—Numerous among Ruppia from Creel Bay. FamMILy CHLAMYDOMONADIDAE Genus Chlamydomonas Ehrenberg, 1833 Chlamydomonas pulvisculus Ehrenberg. Chlamydomonas pulvisculus Ehrenberg, Abh. Akad. Wiss., Berlin, 1833. Occurrence.—Taken from the head of Creel Bay. SUBCLASS DINOFLAGELLIDA ORDER DINIFERIDA FAMILY PERIDINIIDAE Genus Glenodinium Ehrenberg, 1832 Glenodinium pulvisculus Ehrenberg. Glenodinium pulvisculus Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Occurrence.—Taken from the surface and from the ooze at the bottom of Creel Bay. SUBPHYLUM INFUSORIA CLASS CILIATA ORDER HOLOTRICHA FAaMILy ENCHELINIDAE Genus Holophrya Ehrenberg, 1831 Holophrya ovum Ehrenberg. Holophrya ovum Ehrenberg, Die Infusionsthierchen als Volkom- mene Organismen, 1838. Occurrence.—Among algae from Creel Bay. 178 CHARLES HOWARD EDMONDSON, PH.D. Holophrya sp. Figure 13, Plate XVIII. Resembling Holophrya ovum Ehrenberg but much smaller. Length 30-40y. Occurrence.—In the ooze from Creel Bay. Genus Urotricha Claparéde and Lachmann, 1858 Urotricha labiata, new species, Figure 14, Plate XVIII. Description.—Body ovate, about twice as long as broad, equally rounded at both extremities. Cilia covering the entire body, ar- ranged in longitudinal rows and vibrating independently. A very fine seta, nearly as long as the body, extending from the posterior extremity. Mouth anterior, subterminal, beneath a prominent, lobe-like lip. Nucleus central. Contractile vacuole posterior. Reproduction by transverse fission. Length of body about 30g. Occurrence.—Taken from numerous localities in Devil’s Lake. Genus Prorodon Ehrenberg, 1833 Prorodon teres Ehrenberg. Prorodon teres Ehrenberg, Die Infusionsthierchen als Volkom- mene Organismen, 1838. Occurrence.—Among Ruppia and algae of Big Mission Lake and the main lake. Prorodon edentatus Claparéde and Lachmann. Prorodon edentatus Claparéde and Lachmann, Etudes sur les Infusoires et les Rhizopodes, 1858. Occurrence.—Infusions of Ruppia from Big Mission Lake and Minnewaukon Bay. Prorodon griseus Claparéde and Lachmann. Prorodon griseus Claparéde and Lachmann, Etudes sur les Infu- soires et les Rhizopodes, 1858. Occurrence.—Taken from Stump Lake only. Genus Enchelys Ehrenberg, 1838 Enchelys sp. Figure 15, Plate XVIII. Length from 15-20u. Occurrence.—Ooze from the main lake and from the overflow of lake water from the fish-tank. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 179 Genus Spathidium Dujardin, 1841 Spathidium spatula Dujardin. Spathidium spatula Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Among algae from the head of Creel Bay. Spathidium sp. Figure 16, Plate XVIII. A very long, narrow and flattened form. Length 120y. Occurrence.—Taken from infusions from the head of Creel Bay. Spathidium sp. Figure 17, Plate XVIII. A much shorter form than the preceding, with a conspicuous collar about the oral extremity. Length 30y. Occurrence.—From the ooze of the main lake. Undetermined Genus® Undetermined species. Figures 1, 2, Plate XIX. Description.—Body elongate, plastic, slightly compressed dorso- ventrally, inflated posteriorly, narrow anteriorly, rounded at both extremities; cilia of uniform length arranged in longitudinal rows, covering the entire surface; aperture a narrow slit diagonally placed, sub-terminal; contractile vacuole posterior; nucleus concealed; endo- plasm completely filled with green chloroplasts. Length 90y. Occurrence.—From the surface of the main lake and from among Ruppia and algae. Genus Chaenia Dujardin, 1841 Chaenia teres Dujardin. Chaenta teres Dujardin, Histoire Naturelle des Zoophytes Infu- soires. 1841. Occurrence.—Among algae from the head of Creel Bay. Genus Mesodinium Stein, 1862 Mesodinium pulex (Claparéde and Lachmann). Halteria pulex Claparéde and Lachmann, Etudes sur les Infu- soires et les Rhizopodes, 1858. Occurrence.—A common form on the surface and in the ooze of the main lake. 8 The form is treated here with doubt as to its taxonomic position. 180 CHARLES HOWARD EDMONDSON, PH.D. Genus Didinium Stein, 1859 Didinium nasutum (Miller). Vorticella nasutum Miiller, Animalcula Infusoria Fluviatilia et Marina, 1786. Occurrence.—Among Ruppia from Minnewaukon Bay, Whipple Bay, and from the east side of the main lake. Genus Lacrymaria Ehrenberg, 1830 Lacrymaria olor Ehrenberg. Lacrymaria olor Ehrenberg, Abh. Akad. Wiss., Berlin, 1830. Occurrence—Among Ruppia in Creel Bay. Lacrymaria truncata Stokes. Lacrymaria truncata Stokes, Ann. and Mag. Nat. Hist., June, 1885. Occurrence.—Among Ruppia from the north end of the main lake. Lacrymaria cohnii Kent. Lacrymaria cohnii Kent, A Manual of the Infusoria, 1881-1882. Occurrence.—In an infusion from Stump Lake. Lacrymaria lagenula Claparéde and Lachmann. Lacrymaria lagenula Claparéde and Lachmann, Etudes sur les Infusoires et les Rhizopodes, 1858. Occurrence.—In ooze from the main lake. Famity TRACHELINIDAE Genus Lionotus Wrzesniowski, 1870 Lionotus fasciola (Ehrenberg). Amphileptus fasciola Ehrenberg, Die Infusionsthierchen als Vol- kommene Organismen, 1838. Occurrence.—Abundant in many parts of the main lake, also taken from Stump Lake and Big Mission Lake. Lionotus sp. Figure 3, Plate XIX. A very small species. Length about 40u. Often seen in conjuga- tion. Occurrence.—Among algae from Creel Bay. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 181 Genus Amphileptus Ehrenberg, 1830 Amphileptus meleagris (Ehrenberg). Trachelius meleagris Ehrenberg, Die Infusionsthierchen als Vol- kommene Organismen, 1838. Amphileptus meleagris Claparéde and Lachmann, Etudes sur les Infusoires et les Rhizopodes, 1858. Occurrence.—Taken in Stump Lake and from algae at the head of Creel Bay. Famity CHLAMYDODONTIDAE Genus Nassula Ehrenberg, 1838 Nassula rubens (Perty). Cyclogramma rubens Perty, Zur Kenntniss kleinster Lebensformen in der Schweiz, 1852. Nassula rubens Claparéde and Lachmann, Etudes sur les Infu- soires et les Rhizopodes, 1858. Occurrence.—From the overflow of lake water from the fish-tank near the Station. Nasula ornata Ehrenberg. Nasula ornata Ehrenberg, Die Infusionsthierchen als Volkom- mene Organismen, 1838. Occurrence.—Taken from Lake ‘‘N”’ only. Genus Chilodon Ehrenberg, 1833 Chilodon cucullulus (Miiller). Colpoda cucullulus Miller, Animalcula Infusoria Fluviatilia et Marina, 1786. Occurrence.—Infusions of algae from Creel Bay, Big Mission Lake, and Whipple Bay. Chilodon caudatus Stokes. Chilodon caudatus Stokes, Am. Jour. Sci. 29, April, 1885. Occurrence.—Among Ruppia from Minnewaukon Bay. Genus Aegyria Claparéde and Lachmann, 1858 Aegyria pusilla (?) Claparéde and Lachmann. Aegyria pusilla Claparéde and Lachmann, Etudes sur les Infu- soires et les Rhizopodes, 1858. Occurrence.—Among algae near the Station. 182 CHARLES HOWARD EDMONDSON, PH.D. FAMILY CHILIFERIDAE Genus Glaucoma Ehrenberg, 1830 Glaucoma scintillans Ehrenberg. Glaucoma scintillans Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Occurrence.—In algae infusion from near Brannon’s Island. Glaucoma margaritaceum (Ehrenberg). Cyclidium margaritaceum Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Cinetochilum margaritaceum Perty, Zur Kenntniss_ kleinster Lebensformen in der Schweiz, 1852. Occurrence.—Very abundant. From the ooze of Creel Bay, the surface of Creel Bay, Stump Lake, and near Brannon’s Island in the main lake. Genus Leucophrys Ehrenberg, 1830 Leucophrys patula (Miller). Trichoda patula Miiller, Animalcula Infusoria Fluviatilia et Marina, 1786. Occurrence.—One specimen only observed, from the east side of the main lake. A very typical specimen. Genus Frontonia Ehrenberg, 1538 Frontonia leucas Ehrenberg. Frontonia leucas Ehrenberg, Die Infusionsthierchen als Volkom- mene Organismen, 1838. Occurrence.—Taken from the east side of the main lake and from East Lake. Abundant in Six-mile Bay and Minnewaukon Bay. Genus Loxocephalus Eberhard, 1868 Loxocephalus granulosus Kent. Loxocephalus granulosus Kent, A Manual of the Infusoria, 1881— 1882. Occurrence.—Taken only in the ooze of Big Mission Lake near the in-seepage of fresh water. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 183 Genus Uronema Dujardin, 1841 Uronema marinum Dujardin. Uronema marinum Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—One of the most common species in the lake. Abundant everywhere both at the surface and in the ooze. Genus Colpidium Stein, 1868 Colpidium putrinum Stokes. Colpidium putrinum Stokes, Ann. and Mag. Nat. Hist. Feb., 1886. Occurrence.—From algae at the east side of Creel Bay. Genus Tillina Gruber, 1879 Tillina saprophila Stokes. Tillina saprophila Stokes, Am. Nat., Feb., 1884. Occurrence.—Taken only in the overflow of lake water from the fish-tank near the station. FAMILY PARAMAECIDAE Genus Paramaecium Miiller, 1786 Paramaecium trichium Stokes. Paramaecium trichium Stokes, Am. Naturalist, 19, May, 1885. Occurrence.—From near the mouth of a sewer at the head of Creel Bay, and from ooze near the rock pile in the main lake. Paramaecium caudatum Ehrenberg. Paramaecium caudatum Ehrenberg. Die Infusionsthierchen als Volkommene Organismen, 1838. Occurrence.—Taken from Big Mission Lake near the in-seepage of fresh water. FAMILY PLEURONEMIDAE Genus Cyclidium Ehrenberg, 1838 Cyclidium glaucoma Ehrenberg. Cyclidium glaucoma Ehrenberg, Die Infusionsthierchen als Vol- kommene Organismen, 1838. Occurrence.—Abundant everywhere, at the surface and in the ooze in all parts of the lake. 184 CHARLES HOWARD EDMONDSON, PH.D. Cyclidium litomesum Stokes. Cyclidium litomesum Stokes, Am. Monthly Micro. Jour., 6, Dec. 1884. Occurrence.—Numerous in infusions from the head of Creel Bay and in the ooze from the main lake. Genus Pleuronema Dujardin, 1841 Pleuronema chrysalis (Ehrenberg). Paramaecium chrysalis Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Pleuronema crassa Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Observed in infusions from Stump Lake only. ORDER HETEROTRICHA FAMILY PLAGIOTOMIIDAE Genus Metopus Claparéde and Lachmann, 1858 Metopus sigmoides (Miiller). Trichoda sigmoides Miller, Animalcula Infusoria Fluviatilia et Marina, 1786. Occurrence.—Common in dredged material from Minnewaukon Bay, Creel Bay, and the main lake. Abundant in East Lake. Genus Spirostomum Ehrenberg, 1835 Spirostomum ambiguum Ehrenberg. Spirostomum ambiguum Ehrenberg, Abh. Akad. Wiss., Berlin, 1835. Occurrence.—Observed in dredged material from Creel Bay. FAmILy HALTERIDAE Genus Halteria Dujardin, 1841 Halteria grandinella (Miiller). Trichoda grandinella Miiller, Animalcula Infusoria Fluviatilia et Marina, 1786. Halteria grandinella Dujardin, Histoire Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Common in infusions of Ruppia and algae from Whipple Bay and Creel Bay and in the ooze of the main lake. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 185 ORDER HYPOTRICHA FAMILY OxYTRICHIDAE Genus Uroleptus® Ehrenberg, 1831 Uroleptus agilis Englemann. Uroleptus agilis Englemann, Zeit. Wiss. Zool., Bd. 11, 1861. Occurrence.—From the ooze of the main lake, also from Six-mile Bay. Uroleptus rattulus (?) Stein. Uroleptus rattulus Stein, Der Organismus der Infusionsthiere, 1859. Occurrence.—Among Ruppia from Whipple Bay. Genus Oxytricha® Ekrenberg, 1830 Oxytricha fallax Stein. Oxytricha fallax Stein, Der Organismus der Infusionsthiere, 1859. Occurrence.—Among algae from Creel Bay. Oxytricha pellionella (Miiller). Trichoda pellionella Miller, Animalcula Infusoria Fluviatilia et Marina, 1786. Oxytricha pellionella Ehrenberg, Die Infusionsthierchen als Vol- kommene Organismen, 1838. Occurrence.—Taken from Ruppia near the Station, Big Mission Lake, Whipple Bay, north end of Creel Bay, and the ooze from the fish-tank after being flooded by lake water. Oxytricha parvistyla Stein. Oxytricha parvistyla Stein, Der Organismus der Infusionsthiere, 1859. Occurrence.—Among Ruppia near the Station. Oxytricha bifaria Stokes. Oxytricha bifaria Stokes, Ann. and Mag. Nat. Hist., Aug., 1887. Occurrence.—Abundant in Creel Bay, also taken from Whipple Bay. * Further study would, no doubt, result in the determination of other species of the genus than those listed. 186 CHARLES HOWARD EDMONDSON, PH.D. Genus Histrio Sterki, 1878 Histrio erethysticus Stokes. Histrio erethysticus Stokes, Proc. Am. Philos. Soc, 24; 126, 1887. Occurrence.—Among Ruppia from near the Station. Genus Stylonychia Ehrenberg, 1830 Stylonychia notophora Stokes. Stylonychia notophora Stokes, Ann. and Mag. Nat. Hist. June, 1885. Occurrence.— With algae from Creel Bay. Genus Holosticha Wrzesniowshi, 1877 Holosticha vernalis (?) Stokes. Holosticha vernalis Stokes, Ann. and Mag. Nat. Hist., Aug., 1887. A form bearing considerable resemblance to Stokes’ species was occasionally observed. Length 140y. Occurrence.—Among Ruppia from the main lake. Genus Pleurotricha Stein, 1859 Pleurotricha lanceolata (Ehrenberg). Stylonychia lanceolata Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Pleurotricha lanceolata Stein, Der Organismus der Infusionsthiere, 1859. Occurrence.—Taken at the head of Creel Bay. Genus Tachysoma Stokes, 1887 Tachysoma parvistyla Stokes. Tachysoma parvistyla Stokes, Ann. and Mag. Nat. Hist. Aug., 1887. Occurrence.—Observed in infusions from Stump Lake only. FAMILY EUPLOTIDAE Genus Euplotes Ehrenberg, 1831 Euplotes charon (Miiller). Trichoda charon Miller, Animalcula Infusoria Fluviatilia et Marina, 1786. Euplotes charon Ehrenberg, Die Infusionsthiere als Volkom- mene Organismen, 1838. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 187 Occurrence.—Abundant among infusions of Ruppia and algae from many parts of the main lake, and also from East Lake. Euplotes patella (Miiller). Kerona patella Miiller, Animalcula Infusoria Fluviatilia et Marina, 1786. Euplotes patella Ehrenberg, Die Infusionsthiere als Volkommene Organismen, 1838. Occurrence.—Found in Stump Lake, Big Mission Lake, East Lake and in numerous localities in the main lake. Genus Aspidisca Ehrenberg, 1830 Aspidisca costata (Dujardin). Coccudina costata Dujardin, Histore Naturelle des Zoophytes Infusoires, 1841. Occurrence.—Taken in Whipple Bay; numerous among Ruppia in Minnewaukon Bay and also on the east side of the main lake. ORDER PERITRICHA FAMILY VORTICELLIDAE Genus Vorticella Linnaeus, 1767 Vorticella telescopica Kent. Vorticella telescopica Kent, a Manual of the Infusoria, 1881-1882. Occurrence.—Among Ruppia at the north end of the main lake. Vorticella convallaria Linnaeus. V orticella convallaria Linnaeus, Systema Naturae, Ed. 12, 1767. Occurrence.—Attached to diatoms in the main lake, also among Ruppia in Big Mission Lake. Vorticella octavo Stokes. Vorticella octavo Stokes, Ann. and Mag. Nat. Hist., June, 1885. Occurrence.—Among Ruppia at the north end of the main lake. Vorticella microstoma Ehrenberg. Vorticella microstoma Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Occurrence.—Taken at the east side of the main lake. 188 CHARLES HOWARD EDMONDSON, PH.D. Vorticella sp. Figure 4, Plate XIX. A very common form, resembling Vorticella rabdostyloides Kellicott but is considerably smaller and the body is transversely striated. Length of stalk 124, with the diameter of the body nearly the same. Occurrence.—Attached to floating diatoms. Vorticella sp. Figure 5, Plate XIX. A species with more elongate body than the preceding but also transversely striate. Length of body 28y, stalk 68y. Occurrence.—Attached to floating diatoms. Genus Gerda Claparéde and Lachmann, 1858 Gerda annulata, new species. Figure 10, Plate XIX. Description.—Body elongated, cylindrical, of nearly equal diameter throughout, curved when extended; surface finely striate transversely; a prominent annular ridge present usually about one- fourth the distance from the posterior extremity; peristome border revolute, disc slightly elevated; contractile vacuole conspicuous; nucleus not observed. Length of body, extended, 80u. Occurrence.—Among algae and Ruppia from the north end of the main lake. Genus Epistylis Ehrenberg, 1830 Epistylis plicatilis Ehrenberg. Epistylis plicatilis Ehrenberg, Die Infusionsthierchen als Vol- kommene Organismen, 1838. Occurrence.—From the east side of Creel Bay. Epistylis branchiophila Perty. Epistylis branchiophila Perty, Zur Kenntniss kleinster Lebensfor- men in der Schweiz, 1852. Occurrence.—Among algae near the head of Creel Bay. Genus Carchesium Ehrenberg, 1838 Carchesium epistylidis Claparéde and Lachmann. Carchesium epistylidis Claparéde and Lachmann, Etudes sur les Infusoires et les Rhizopodes, 1858. Occurrence.—Among algae from Creel Bay. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 189 Genus Zoothamnium Ehrenberg, 1838 Zoothamnium alterans Claparéde and Lachmann. Zoothamnium alterans Claparéde and Lachmann, Etudes sur les Infusoires et les Rhizopodes, 1858. Occurrence.—Among Ruppia and algae from Stump Lake. Zoothamnium sp. Figure 6, Plate XIX. Stalk very stout, zooids smooth, usually 2-8 in a colony. Length of stalk 216y, of zooid 64y. Occurrence.—From Stump Lake, East Lake, Creel Bay, Whipple Bay, and from the main lake. Attached to algae or Ruppia. A fairly common form. Genus Vaginocola Lamarck, 1816 Vaginocola crystallina Ehrenberg. Vaginocola crystallina Ehrenberg, Die Infusionsthierchen als Volkommene Organismen, 1838. Occurrence.—Numerous among algae from East Lake, also taken from Stump Lake and from the north end of the main lake. Genus Cothurnia Ehrenberg, 1831 Cothurnia imberbis Ehrenberg. Cothurnia imberbis Ehrenberg, Die Infusionsthierchen als Vol- kommene Organismen, 1838. Occurrence-—Commonly attached to floating diatoms, from dredged material and also among Ruppia in Creel Bay. Also taken from Stump Lake. Cothurnia curva Stein. Cothurnia curva Stein, Der Organismus der Infusionsthiere, 1859. Occurrence.—Among Ruppia at the north end of the main lake. CLASS SUCTORIA FAMILY PODOPHRYIDAE Genus Podophrya Ehrenberg, 1838 Podophrya libera Perty. Podophrya libera Perty, Zur Kenntniss kleinster Lebensformen in der Schweiz, 1852. Occurrence.—Numerous at east side of the main lake. 190 CHARLES HOWARD EDMONDSON, PH.D. Podophrya sp. Figure 9, Plate XIX. Bears some slight resemblance to Podophrya cyclopum Claparéde and Lachmann. The lobulated border may have represented a reproductive phase or possibly was abnormal. Total height 60y, stalk 20u. Occurrence.—Attached to algae from the main lake. Several specimens were observed by Dr. R. T. Young. Genus Sphaerophrya Claparéde and Lachmann, 1858 Sphaerophrya magna Maupas. Sphaerophrya magna Maupas, Arch. de Zoologie Experimentale, tom 9, Nov., 1881. Occurrence.—From Stump Lake and the east side of the main lake. FAMILY ACINETIDAE Genus Acineta Ehrenberg, 1838 Acineta sp. Figure 7, Plate XIX. Body triangular in broad view, compre sed; endoplasm very granular, nucleus concealed. Total height 50yu, stalk 20u. This species resembles, in some degree, Acineta lemnarum Stein. Occurrence.—From floating material in the main lake and also among algae from Stump Lake. Acineta sp. Figure 8, Plate XIX. Body oval, slightly broader distally, greatly compressed; endo- plasm granular concealing the nucleus and contractile vacuole. Total height 60-72y, stalk about 15y. Occurrence.—Attached to algae from Stump Lake. Commonly feeding on Uronema. 3. EXPERIMENTS Preliminary experiments in transferring protozoa from fresh water to the con- centrated water of Devil’s Lake and vice versa. In order to test the reactions of certain protozoa taken from other sources to the more concentrated waters of Devil’s Lake a series of simple experiments were carried out by which forms of protozoa common to fresh water were transferred directly into the more saline water of the lake. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 191 Infusions from a small body of fresh water near the southern boundary of the main lake were prepared and certain protozoa which readily appear in cultures were used in the tests. By placing a drop of the fresh water culture on one end of a micro- scopic slide and a drop of lake water near the middle of the slide and, with a needle, drawing out from each drop toward the other a narrow channel of water until the two met, the protozoa were conducted from the fresh water drop into that of the lake water. To eliminate possible influence of the fresh water a series of drops of lake water were used and the organisms rapidly transferred from one to the other until they reached a pure medium of lake water. The waters from the two sources were kept at a uniform tempera- ture and the effect of the change of environment thus brought about was carefully noted by the activity of the organisms. In similar manner the transference of certain protozoa from lake water to fresh water was accomplished and the effect of such change observed as hereinafter noted. A. Transference of protozoa from fresh water to lake water. 1. Paramaecium sp. A specimen of a species, probably Paramae- cium caudaium Ehrenberg, commonly occurring in the fresh water was removed to the pure lake water with the following results: An immediate change occurred in the organism. The body became greatly compressed dorso-centrally with erratic movements at first which soon gave way to a more steady, forward movement with slow rotations on the long axis. A noticeable change also occurred in the contractile vacuoles. The normal rhythmic collapse of the vacuoles ceased after a few minutes and they became greatly dilated and dis- torted. After ten minutes of rotary movements the organism became quiet with the cilia of the periphera and the oral groove still active. Many non-contractile vacuoles filled the endoplasm. Death occurred at the end of twelve minutes. A second specimen, after showing the same flattening of the body, moved in circles for six minutes then assumed the forward movement with rotations on the long axis. In eighteen minutes the organism became quiet with a highly vacuolated endoplasm and the cilia of the oral groove vibrating feebly. Death occurred in twenty-six minutes. 192 CHARLES HOWARD EDMONDSON, PH.D. A third specimen after exhibiting similar physical and physiologi- cal changes came to complete rest in twenty-two minutes. Death resulted in twenty-five minutes. A fourth specimen showed similar responses and died in fifteen minutes. Seven specimens were then transferred at the same time. Six of these, after exhibiting similar responses as the preceding, were dead at the end of ten minutes. One, after reacting in like manner, died at the end of eighteen minutes. 2. Stylonychia sp. Several tests with a species of Stylonychia were carried out. Unusual responses were less quickly manifested by Stylonychia than Paramaecium when brought into contact with the lake water. Commonly after five or six minutes of normal movements a rapid whirling over and over of the body occurred gradually sub- siding into complete rest. Death occurred in all specimens in from sixteen to thirty-two minutes. Reactions of similar character were obtained from Paramaecium and Stylonychia by the introduction of small quantities of NaCL into the fresh water in which they were normally living. 3. Metopus sp. A short type of Metopus, common in fresh water, was transferred to the saline lake water. The most noticeable change was an almost immediate flattening of the body. Normal rotary movements continued for eight minutes when the organism came to rest with the cilia of the surface still more or less active. Death occurred at the end of fifteen minutes. Numerous individuals of this species were used in successive experiments with reactions similar in each case. Death resulted in all specimens in from eleven to eighteen minutes. B. Transference of protozoa from the concentrated lake water to fresh water. 1. Uroleptus sp. The form used was one of the elongated types. More than sixty specimens were used in the tests. With few excep- tions but with considerable degree of variation, the following reactions were very evident: After a period of from ten to fifteen minutes contact with the fresh water, during which time more or less normal activities were maintained, the organisms came to rest with the cilia still in motion. The cell bodies became shortened and dilated, in PROTOZOA OF THE DEVIL’S LAKE COMPLEX 193 many instances assuming a spherical form. After enduring this state of depression for from ten to fifteen minutes the organisms showed signs of recovery. The bodies gradually assumed an elongated form and normal activities reappeared. Within a period of one hour and twenty-five minutes from the time the organisms were first introduced into the fresh water all, with the exception of a few which failed to survive the state of depression, had fully recovered and were respond- ing in a normal manner. Considerable variation in the effect of the change was noted. Of those surviving some were slightly affected and wholly recovered in forty-five minutes, some in sixty minutes, while others required the longer time noted above. 2. Euplotes patella (Miiller). Numerous individuals of this spe- cies were transferred as in the preceding experiment. The effect in this case was an immediate one. As soon as contact was made with the fresh water the cell bodies became swollen and distorted, losing the longitudinal striations and all resemblance to normal individuals. During this state of depression the organisms were at rest with the cirriin feeble motion. After a period of fifteen minutes the cells began to resume movements although in a distorted condition. In fifteen minutes more the longitudinal striations reappeared and soon after normal responses were entirely restored. 3. Uronema marinum Dujardin. The transferrence of this spe- cies from the lake water to fresh water resulted in no apparent state of physical depression and no diminished or unusual responses to stimuli could be detected. The species is commonly recognized as both a marine and fresh water form. 4. SUMMARY AND CONCLUSIONS SUMMARY OF THE Groups OF PROTOZOA RECORDED SEVIS GIL REAM A aC dent NS 13 species Mash OWNOnAt sage mwa wee ety (OS ks Ne Dew nr PURELY yr, wh Sk ater eRe EE) toy fo Fea Leese t ee A 0 111 species Conclusions 1. The proportion of the number of species of the three groups of protozoa recognized in Devil’s Lake corresponds favorably with the same in a typical fresh water lake. 194 CHARLES HOWARD EDMONDSON, PH.D. 2. A most noticeable feature of the study of this fauna is the apparent total absence of numerous forms universally found in fresh water. The dearth of shell-bearing rhizopods was mentioned in the introduction. Many common species of flagellates and ciliates were, at no time during the survey, observed in the concentrated waters of the lake. 3. The subdivisions of the classes of protozoa are fairly well represented in Devil’s Lake. Two new species are described in the report but with the exception of the facts mentioned in the preceding paragraph, the protozoan fauna of Devil’s Lake cannot be considered an unusual one. 4. Experiments of the interchange of protozoa between fresh water and the lake water seem to indicate that the organisms of the lake may adjust themselves to fresh water conditions with more readiness than can the forms accustomed to a fresh water environ- ment accommodate themselves to the concentrated water of the lake. PROTOZOA OF THE DEVIL’S LAKE COMPLEX 195 5. INDEX PAGE PAGE PNGIAE UA tes coaipechehel mata GHEE LOOT Chaentarys syne ate errr ieee z caren 179 Acineta lemnarum..........0004: 190 i Chaentateresine jarnciceyee mice eee 179 PRENTIE CAS) «scene ais eiefeteiedn ae ie eel ove 1900 (eC@hiliferidaenasie iss sey eaieiscs: 182 UN STITT Eye se Ea 190) xiChilodontscuseeie aoe eee aes 181 EMEDTV Ss /sic als uite yee eo 17S ea Chilodonicaudatusss-5epeaeerieee 181 Mammophrys Sol... 4.65.6. 6 fe a6. 173% Chilodonjcuculluluss:oicceseo. sa 181 PRENSA ah srs s yo) 2b ovsseos't fencha Sisi dean 6 {Si Chiamydodontidaeya yy... 12a 181 PME MMUR SIN. eas sins a sce ce cise 181 Chlamydomonadidae............. 177 a STR IEL 3 pth eck Aah SIRE Ba a Pie Chlamydomonas.\s3, 5 ssa ae 177 OS PUL EELT ETE oe SL I a 171. Chlamydomonas pulvisculus...... 177 Amoeba guttula... 0.0... ee 12) -Chioroflagellidan ty) (oV. 08 alse) sare 176 Snare @layn lian lets eles ceva ae eee ena ae Ae/hattt Cilia taney ema pies eet everie to krnnyay Cay 177 MME AVATOLEUS 1.66 ooh es we as 171 Cinetochilum margaritaceum....... 182 PUINGEDATACHIOSA. coco c ick leone: ilg(al COCCUAINGIGOSIDIAs ak oe eee 187 ie na Stbiata..oo: =. -ee see 182 Loxocephalus granulosus......... 182 Mastigophora ......:.:-.-=eeeeee 173 Mesodinium:. .. - 2): ... 0c) eee 179 Mesodinium pulex.............-. 179 Metopus:......-5.+:s5.5¢s eee 184 Metopus sigmoides.............. 184 Metopus Sp-1....2.554 4 -= eee 192 Monadidas o:.. oc... «ae 173 Monas. 2.00.65) +0 25 lense 173 Monas fluida. ..... +). v.72 eee 173 Monas tirregularis...........+.+-: 174 Monas sp.'......... 5-05 ++. 5-5 Wassula..iis. asc ns cst oh See 181 Nassula.omata:. -\nn4-4 eee 181 Nassula, rubens)...\-2.- tera 181 PROTOZOA OF THE DEVIL’S LAKE COMPLEX PAGE INGtosGlenluSs +) shktn te etaee sheen 176 INGEGSOIENUS SPy sc. s. desk see ok 176 PUBATUINGM BS 5 oi- y.os\ anc oes nhc eee 185 Oxytricha bifaria....... PS RN evel 185 Rerviricha fallax... ou kee 2 te 185 Oxytricha parvistyla............. 185 Oxytricha pellionella............. 185 DRPPSTICRIGAG. 2c. c.5.c'i ye ehieale et 185 IPAPAIMAECICAG. oa. o¢ Acre eciere Ss 183 PED GL TENGE Ue ree ee 183 Paramaecium caudatum.......... 183 Paramaccium chrysalis........... 184 PAGATAACCIUM SP), 2.4: 653 seit ec 191 Paramaecium trichium........... 183 Peranemildae:,. 2, 266, ca ee 175 BEICINUICAC ss walt ods Ged eitiva yes 177 [PEDAL LSE yagi ees CE oe eee 187 Rate eTMOMAS 4 cys c soe cheno sels = 175 Petalomonas ervilia.............5. 176 Petalomonas mediocanellata...... 175 IREtAlOMONASISP. fc w- feler ci ee sos 176 EAERGUISME PE Cars sie aia isiase < echals ie Da" 175 _ GTS Te) (hr ee 175 Pimephales promelas.............. 170 SM MIOLOMMNICAC. 2... cis eee ee 184 pleRTONC MIA. = Joos. 08k YeNlee vee 184 Pleuronema chrysalis............ 184 PIEUPONCMG GROSSE..5) 06. ae es 184 PISUTOHENNGCAC 4. 5\).0) << + os os ales 183 TSLiS( Lr ate) JE che Bore eRe eee 186 Pleurotricha lanceolata........... 186 PGMOP HEYA.) slisiases micas aie da weik 189 Podophrya cyclopum...........4. 190 Podophryaidibera.). 325 oes: 189 PodOphTVya/ SP isaac oN 190 Paaophnviddes ya) csNsk sae cones 189 PMSA: 2 os eee 174 Wemrmnstigidae, ........).02 4304.55 174 [ELS S STaE re aie Seat ee Pe ee ae 176 Polgtomauyella. ..2.)3 02022-46284 176 OMvUON Ae) <5 2 Fe cise leieees 176 212100 7514 Sl A eam tr AS Be 178 Prorodon edentatus.............. 178 PAGE Prorotion griseus. 5 see ae ee 178 PHOFOdOM COLES iA fi.) rete ela lene Sie ore 5 178 Rand pipens ntl ee. Ue ss. . 170 Rhizomastigidaey noted. 3: 173 Rn ZOPOGane eee ia ee aie ere oe 171 Sarcadina® . ix Messen a aadioraes 171 Spathidium\2c ost jase eae oe aes 179 Spathidium spatula.............. 179 Spathidinga, Sp... nce Deen 179 Sphacrophrya. tinier seater ose 190 Sphaerophrya magna............ 190 SPUTOS LOMA fde aces avec chert tere ate 184 Spirostomum ambiguum.......... 184 Stylomyebia wai Ces aerate! aebaren 186 Stylonychia lanceolata...........- 186 Stylonychia notophora........... 186 Styonycelarspep les ierteiale eek < setae 192 Suctoriayeay vee mers scan arate te 189 PachySomay tosses winks cetots 186 Tachysoma parvistyla............ 186 Mestaccak eines Mes Fo os ete 172 Wetranmtidaen ss ove tae see ee 176 Metraselmist 4: eee crmynia canna 176 Tetraselmis cordiformis.......... 176 Sling ees fe oncee ese iai neers 183 Tillina sapropuila. 2 \'oa so. 183 ibrachelinidacwnn secure rte cert 180 Trachelius meleagris.............. 181 Trachelius tricophorus..........-+ 175 ARE PYOIMIONAS sche each delete 174 Trepomonas agilis............... 174 Dir tChedanGharowd sn lelte elena 186 Trichoda grandinella............. 184 DRUGhOMON PAULL Gs aoe ali sh ee 8 182 Trichoda pellionella.........-.... 185 Trichoda sigmoides..........-+.+:: 184 ‘Atintncuahien ae pacnoue cosedeo we 177 Undetermined genus............ 177,179 Undetermined species.........-. 177,179 Wired erat ese cha)y d'=\Ggha ls te acess 2 = 185 Berle bs) AIMS io )4) iia) s/ ¢ slates cleo mie 185 198 PAGE Uroleptus rattulus ), -2)..cis1 ip oe 185 Wroleptusispe:scscut > es Mecerp eee 192 Wronemaracwiat oy coccser eer eeee 183 Uronema marinum...........:.- 183 Wrotnchal tees ce eee 178 Urotnichaylabiatay oper -ee eee 178 WVarinocolane a.iescciic oieceeee 189 Vaginocola crystallina............ 189 Wonticella em. aac aceite eee 187 Vorticella convallaria............ 187 Vorticella microstoma............ 187 CHARLES HOWARD EDMONDSON, PH.D. PAGE Vorticella nasutum...........-.-. 180 Worticellajoctavo. =. -- eee 187 Vorticella rabdostyloides........... 188 Vorticella sp. 7. o< 31. i. eee 188 Vorticella,telescopica. i522. -ee8 187 Vorticellidaé:,..c.:... 2528. tt eee 187 Zoomastigophora. «7-255. 2 ees 173 Zoothamnitimeses sree ee eee 189 Zoothamnium alterans........... 189 Zoothamninmisp...).).2 coe 189 EXPLANATION OF PLATES Prate XVIII Figs. 1-3. Cercomonas sp. x 1090. Figs. 4,5. Monassp. x 750. Fig. 6. Heteromita sp. x 2000. Fig. 7. Monas sp. «x 1200. Fig. 8. Monas sp. x 1500. Fig. 9. Notosolenus sp. x 900. Fig. 10. Petalomonas sp. x 600. Figs. 11, 12. Undetermined genus and sp. x 1250. Fig. 13. Holophrya sp. x 550. Fig. 14. Uronema labiata, new sp. x 750. Fig. 15. Enchelys sp. x 1200. Fig. 16. Spathidium sp. x 300. Fig. 17. Spathidium sp. x 900. (Posterior seta omitted in figure.’ PLATE XIX Figs. 1, 2. Undetermined genus and sp. x 380. Fig. 3. Lionotus sp. x 800. Fig. 4. Vorticella sp., including stalk. x 800. Fig. 5. Vorticella sp., including stalk. x 350. Fig. 6. Zoothamnium sp., including stalk. x 250. Fig. 7. Acineta sp., including stalk. x 400. Fig. 8. Acineta sp., including stalk. x 280. Fig. 9. Podophrya sp., including stalk. x 370. Fig. 10. Gerda annulata, new species. x 500 To TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY OILS FOODS PLATE XVIII EDMONDSON g (9% TRANSACTIONS OF THE AMERICAN MICROSCOPICAL SOCIETY VOL. XX XIX PLATE XIX EDMONDSON AGE, GROWTH AND SCALE CHARACTERS OF THE MULLETS, MUGIL CEPHALUS AND MUGIL CUREMA BY ARTHUR PAUL JACOT CONTENTS PAGt Lol -SUNCUNTDS 5 Ss0.016 2c RIGA nN a ee PREIS. Aur Weer ee ROE cg 199 MR TENET OLEOU SPECIES re fo. 0.0) 88s Pe nce che Ie ee Se a Ce RL a eee 200 SU mA ceL TU SMIENINT Crete tetra rotor ee ot. Neila. ua lle eat eee a itne) oct. sled te Renan eyalnas 204 MPa PRGENMAIOLMOI My OUR Le oi). ee elar selec rec oeeiaeels es cad sulk Maat taevel eee 204 Mevelopment Of young. =... 2... y...5..... 6% PR Shh ea Tehst i sich eer 204 WIE EIDEITTOERY Sag l SUB Aa Ry cake ne TER At gO en lg ge RU EAD RD Ae 214 BENE EC EOS LOUP Am mit tie cont my ent wets 66 200 DEPARTMENT OF METHODS 201 Rather unfortunately, because the author does not seem to have a large first-hand knowledge of investigation on inheritance, the book is introduced by a somewhat rambling and inconsequential jumble of illus- trations and exhortations which is rather euphemistically labeled ‘‘Envi- ronment and Heredity,’”—presumably because these terms combined make room for about all that can be said on any subject. An analogous loose- ness and lack of system in arrangement mars the treatment at many points and leads to much unnecessary repetition, and to some seeming conflicts. This is particularly illustrated in comparing chapter 3, The Introduction to the Story of the Endocrines; chapter 4, Internal Secretions, and chapter 18, The Balance between the Endocrines. The total is something like what one might use in a series of lectures on the subject to a class in which inattention or lack of preparation would make much restatement seem necessary, rather than what one expects in a scientific book. Aside from those mentioned, the following are the principal chapter headings: Environment and Heredity; The Endocrines in Gynecology; Hypergenitalism and Hypogenitalism; Skin Affections and Internal Secretions; Puberty and Climacterium; The ‘‘Higher up” Theory of Steril- ity in Women; Pregnancy, Labor and Placental Gland; Constitutional Dysmenorrhea; Instincts and Emotions; Mental and Nervous Defects; Mental Deficiency and Criminality; Neuroses and Psychoses; Phobias; The Autonomic Nervous System; Therapeutic Suggestions concerning Endocrines; and several chapters dealing with histories, symptoms, clinics and cases. Possibly an illustration will aid in making vivid the author’s repeatedly emphasized point of the interdependence of the internal secretions. In respect to lactation after labor, the following facts are significant:—The mammary glands are developed at puberty by the interaction of secretions from the ripening ovaries, the posterior hypophysis, the thyroid and the adrenals. A secretion from the ovaries or from the endometrium causes them to swell at menstruation. Placental secretions during pregnancy produce hypertrophy and differentiation of tissue at that time, and seem to inhibit the action of the above mentioned secretions. Milk itself will not form however until this placental secretion is removed or inhibited. After birth the ovaries, posterior hypophysis and other endocrines resume sway and stimulate degenerative process by which milk is formed. Assuming that feminine metabolism and emotional states are more variable and instable than the masculine, the explanation by the endo- crinologist would include such facts as these:—men and women alike possess these numerous glands and with‘all degrees of original potency; all these glands are normally pouring their secretions into the blood constantly; the secretion of each gland modifies those of certain, if not all the other glands, as well as general metabolic conditions thruout the body; the glands, directly 202 T. W. GALLOWAY or indirectly are also modified in their action by the metabolic conditions and by sudden changes of state (as of the emotions) which may be initiated by the environment; gradually under normal conditions and in average individuals these various forces come into an adjustment that represents a person’s constitutional norm; in women 13 times a year there is a cyclical interruption of this balance by the introduction of new factors which influence all the endocrines involved and thus upset the balance; in the case of pregnancy, new secretions (and consequent modification of the endocrine balance and of the mental states dependent upon this) are introduced about each of these points: pregnancy, fetal development, parturition, lactation, and the cessation of lactation. Probably it will be of most service to the readers of this review, in trying to give an idea of the comprehensiveness of the book, to outline the sources, effects and interrelations of the various internal secretions as the author conceives them, especially the more intimate interrelations between the thymus, thyroid, pituitary and the sex glands. The experiments and deductions pointing to, and partially explaining, the cyclical character of these sex-linked endocrine activities seem to the reviewer the most effective and valuable part of the book. The treatment of the sexual and reproductive secretions of the male is not nearly so adequate, in spite of their greater simplicity, as is that of the female. “1v94 Y}J-] Woy sdojaaeq “qoaye Surytqryur sdojs pur ‘Ajiaqnd je ssearse1 SusT[Oqe}aW WNIs]ed saduaNyuy “aDvaf 03 Aqyetoadso spuodsai v[[npe Ww "TasUR YIM payoauU0; . *suoty -owa Aq pastaidul UOl}2I99S “APIATJ -98 I1lay} SasvesioUl AOUPUSeIg -Aoueusaid ul jurjyiodwy *Aj909a1d jequew pue [eoissyg “Spur[s xas Jo JusuIdojaAap szIqiyuy *AJlINJLW I9Y}O puv Xas SUa}SPH *sauog a[Isviy “Joys ‘UIT, “spruogs jo JUaWIdO[aAVp s}IqIyUy] -ysn]q ‘1vay ‘Ajarxuv ‘ssousNOAJAU ‘L[[NpauU jo UOT} RINUIT}S-I9AG) *AS1auUa AvpNosnw ‘asuv ‘asvinod sv ‘satytjenb oulpnosvur s1o py ‘JuawdojaAep Xas puv YYMOIZ sply JO PIWAXO} JsuIVse sjD9}0I1d fansiyvy AP[NosnwW JO} aJopyuy “Aouvusoid ul Auvjoq [vioued 10 VUTIA}:) “WaysAs D1aYIVAUIAS JO AZI[IGISUS SASBAIOUT PUP ‘s[[9d 9AIOU p1}U9D JO APIATIO® sajyesspOU SWIST[OGRJeW UINTI[vd seouanyuy 93k plo UI SassoiZer {Aqioqnd jv aatqoy | YzMoIT [vIIUT sazyVATJOV PUL ‘WISTOGrJIW WUNIS[vd SaoueNyUyT ‘a PUIIy 9Y} JO SATzIeT] -noad ul s}[nsai ‘prorAyy repnp -UP]S PUP U[[Npou [EUdIpe ‘(1P] -NOI[[O}) AIvAO Yim peldnoy ‘QUINYUIS}I UL appmas A[[vIsads ‘sald livtpnoed ajeur saonpoid = proiAy} [v1 19S107 UT puv x9}109 [vuaipe ‘sI}sa} YL “QQUINGUI S}I UI aypu AT[vIDedS "IOW I] SAPIPIGVLAIL “APLIQVILONY ‘ssoulze[ pue ssauysissnys soonpoid ‘yyMois sprrjay jo “oqo ‘vasnvu {paounouoid s1OU SZUT[Iaj XOS svayIOUaLISAC “Aydorje [e}luas Ayiaqnd 194jv Su0y -BNIFSUALL JO UOTJIGIYUL puv WISI]{IJURJUT |eNxes ‘AZaqnd s1ojagq “1OGE] S9}VN}UIIIV PUR UOIJENIJSUIU SayTPOy “Aysodipy ‘s[e}luas puv SN1ajNn 19A0 AT[eIDeds—a ‘jor,;UoD IIYydo1 yz, ‘ayeipAyoqies Aj[etoadsa “wstjoqvjJeu sjosayy ‘OAIQUWUA SAYV]NUIT]S ‘snioyn JUeUBIId 0} 9ATID9}0Ig “SaTPUU UT AQI[VNb auturwmay ‘yustudojaAap auoq Jo uolzIqryuT : “A[esaworor ‘Ayiaqnd 197j¥ ‘sjuvis [PWLION, *AIBAO 0} IIQSTUO -deyue A[proig “sguouli0Y 317 “SIUOZEJUL JVYMIWOS OA} SELEY *O}0 ‘WSI[IJURJUL [eNxas ‘FuyIVMp 0} spraT “‘yuswdojaaap xas pure {e}uat ‘;eoIsAyd saouanguy SMAVNAL SLI MATa IVNOILONOY IVUANAD GNV OINALSAS - “SIS . + -AydodAy 07 djsluoseyue fsnuAyy yy [oto SA GSES SEY CIN T — “s[PuaIpe PUP salIvAO Aq passaidacT + *(ayeu Ul AT[eTOadsa) xas puv ‘[raurd : a ‘prorAyyeied ‘prorAéy} yiLM pazPioossy SOWAHL “Sul ee PI[Npayy +-+ “AQUC CAI A eipas Tele |\es seem eee ete nu ue ***xaqz109 *Aguvuseid ‘\uaudo[aAap puv ‘suvz10 xas Ul st stsAydoddy pur ploidy} gym payeloossy :STVNAUCV *ssauyvam IP[NOSN A at ig EE a “SplorAyy 0} SIYstuoseyUy| ** SGIOMAHLVAVd ; set 3 “snUAY} SaqylOxy “WISTUT}OI19 ‘BULAPPOxATy i “JOY}I9 JO [PAOWAI UO plorAyy vied = pue ptoiAq}y jo AydorsedAy penny “uolyoUN} pur ‘o[Rulay + ar Aprepnoard ‘xas yyIM payeioossy [°° °°" so aianeneiea een CLL CAO; *Aouvuseid isa see “AQUITSYNSUL plo1Ay} YYIM pazPloossy at “OPI! 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ANIMOOGNG AHL tO AOWNOS LIST OF MEMBERS In order to reduce the cost of printing, the complete list of members will be omitted. MEMBERS ADMITTED SINCE THE LAST PUBLISHED LIST Bicknell Anna Bao ere are ote a eho SE eee: 4411 39th St., Washington, D. C. Bierbaum, ‘C. He os. 2 wf obese ee ee cone nes. see. Mutual Life Bldgs Balai eee Boy dent Ac Amer ori hen wre er a eee eee 1421 Oakridge Ave., Madison, Wis. Glevelandwicar: 2by,985 aaecrs coe tee ee 220 W. Monument St., Baltimore, Md. Danheim:_ "Bertha Ee BeSs) ne oe Ro een ree mints Ae a etc Blue Rapids, Kansas. IDERawojn, layabre, IB IMIS IDS Soe eas Ga csan ryolao 5 1512 N. Gratz St., Philadelphia, Pa. Depewer Ganson ia. cries ene ee ois 167 Summer St., Buffalo, N. Y. IDyevevo}. li@eva iin; INU ID Lao eas aacsoocsanaue ose Pea ol ache? Aguila 72, Havana, Cuba. Fellowssitarniettelloaa eycitaee tees 220 S. Prairie Ave., Sioux Falls, South Dakota. Gunns, Cecil A. . Dept. Zoology, Kansas State Agricultural College, Manhattan, Kansas. Fiallitvensepeb eS: (5, Mets creche here 4 oi eT eh ete Cooperton, Oklahoma. Herrick, Chester A., B. S. ... Kansas State Agricultural College, Manhattan, Kansas. Kamal, Mohammed, B. S. ....Kansas State Agricultural College, Manhattan, Kansas. eoftonRNobentibs At fyeeh ey. hoe see cae Bureau of Standards, Washington, D. C. MacKay, Alexander H., A. B., B.Sc. LL.D., F. R.S. Canada Se PRE: Loe er ee: Sa e 61 Queen St?, Dartmouth, Nova Scotia, Canada. Nikevavalveutahee IES ING, Jn Ih yb a 56 dca eomoncaus New York University, New York, N. Y. Rayne nmNelic Vil sno me seen eres 1400 Poyntz Ave, Manhattan, Kansas. Butz Alined hice Mita ct ee oes ses Ree 5117 Locust St., Philadelphia, Pa. Yoo TOS IM JANID Laws dea a eats one 310 W. Monument St., Baltimore, Md. Sister Monica Mie S*e a eee sess Notre Dame Training College, Glasgow, Scotiand. Sperry, Arthur, Bt S) ase Kansas State Agricultural College, Manhattan, Kansas. 206 a INDEX A Abstracts, 14; 89; 158; 190. _ Acanthocephala from the Eel, 1. Ackert, J. E., and Wadley, F. M., Observa- tions on the Distribution and Life History of Cephalobium microbivorum Cobb and of its Host Gryllus assimilis Fabricius, 97. Allen, W. E., Some Work on Marine Phyto- plankton, 177. Allen, W. E., A Brief Study of the Range of Error in Micro-enumeration, 14. American Mullets, Life History and Scale Characters, 26. Animals, Occurrence and Réle of Copper in, 144. Animal Parasites, Compendium of Hosts of, 195. Annual Report of Treasurer, 48. Arrhenuri, New Species and Collections, 168. B Baker, F. C., Preparing Collections of the Mollusca for Exhibition and Study, 31. Bandler, S. W., The Endocrines, a Review, 200. Briefer Articles, 14: 89; 158; 187. Brownian Movement, Microscopical Ilumi- nation with Reference to, 158. Bullard, Chas., A Method for Orienting and Mounting Microscopical Objects in Gly- cerine, 89. G Cambarus agrillicola Faxon, Spring Migra- tion in, 28. Cephalobium microbivorum Cobb, Distribu- tion and Life History, 97. Cnidosporidian Spores, Structures Charac- teristic of, 59. Combination Lighting, Microscope Ilumi- nation with Reference to, 158. Common Field Cricket, A Sarcophagid Par- asite of, 116. Compendium of Hosts of Animal Parasites, 195. Copper, Its Occurrence and Rdéle in Insects and Other Animals, 144. Crayfish, Spring Migration in, 28. Cummins, H., Spring Migration in the Cray- fish, Cambarus agrillicola Faxon, 28. Custodian’s Report for the Year 1920, 47. D Desmid, Method of Demonstrating Sheath Structure, 94. Diatoms, Literature of, 187. Distribution and Life History of Cephalo- bium microbivorum Cobb, 97. E Eel, Acanthocephala from, 1. Endocrines, Review, 200. F Faust, E. C., Larval Flukes from Georgia, 49. Faust, E. C., Recent Advances in Parasit- ology, 75. Fixatives, Effect upon Myxosporidian Spores, i Lee Fresh-water Biology, Ward and Whipple, Compendium of Hosts of Animal Parasites contained in, 195. Fresh-water and Marine Gymnostominan Infusoria, 118. G Galloway, T. W., Review of Endocrines, 200. Georgia, Larval Flukes from, 49. Glycerine, Mounting Microscopical Objects in, 89. Gryllus assimilis Fabricius, Distribution and Life History of, 97. H Hausman, L. A., Fresh-water and Marine Gymnostominan Infusaria, 118. Henderson, W. F., Treasurer, Annual Re- port, 48. Herrick, C. A., A Sarcophagid Parasite of the Common Field Cricket, 116. Hosts of Animal Parasites, A Compendium, 195. Hubbs, C. L., Remarks on the Life History and Scale Characters of American Mullets, 26. 207 208 INDEX I Infusoria, Gymnostominan, 118. Insects, Occurrence and Réle of Copper in, 144. K Kudo, R., On the Effect of Some Fixatives upon Myxosporidian Spores, 161. Kudo, R., On the Nature of Structures Char- acteristic of Cnidosporidian Spores, 59. IU, Larval Flukes from Georgia, 49. Life History and Distribution of Cephalo- bium microbivorum Cobb, 97. Literature of the Diatoms, 187. M Marine and Fresh-water Gymnostominan Infusoria, 118. Marine Phytoplankton, 177. Marshall, Ruth, New Species and Collections of Arrhenuri, 168. Methods, Department of, 14; 89; 158; 187. Method of Demonstrating Sheath Structure of a Desmid, 94. Method for Orienting and Mounting Micros- copical Objects in Glycerine, 89. Micro-enumeration, Range of Error in, 14. Minutes of Chicago Meeting, 47. Microscope Illumination, 158. Mollusca, Preparing Collections for Exhibi- tion and Study, 31. Mounting in Glycerine, 89. Muttkowski, R. A., Copper; Its Occurrence and Réle in Insects and Other Animals, 144. Myxosporidian Spores, Effect of Fixatives upon, 161. O Orienting and Mounting in Glycerine, 89. P Pflaum, M., Custodian, Report for the year 1920, 47. Phytoplankton, Marine, 177. Preparing Collections of Mollusca, 31. ° Proceedings of the Society, 47. R Range of Error in Micro-enumeration, 14. Recent Advances in Parasitology, 75. Reports of Auditing Committee on Treas- urer’s and Custodian’s Reports, 48. Reviews, 14; 89; S Sarcophagid Parasite, 116. Scale Characters in Mullets, 25. Sheath Structure of Desmid, 94. Silverman, A., Microscope Illinination with reference to Brownian Movement and Combination Lighting, 158. Spencer-Tolles Fund, Report on, 47. Summaries, Department of, 75. 4p ~ Taylor, F. B., The Literature of the Diatoms, 187. Taylor, W. R., A Method of Demonstrating the Sheath Structure of a Desmid, 94. Treasurer, Annual Report, of, 48. V Van Cleave, H. J., Acanthocephala from the Hel) 1. Van Cleave, H. J., 4 Compendium of the Hosts of Animal Parasites contained in Ward and Whipple’s Fresh-water Biology, 195. W Wadley, F. M., and Ackert, J. E., Distribu- tion and Life History of Cephalobium mi- crobivorum, 97. Ward and Whipple, Compendium of Hosts of Animal Parasites, 195. Welch, P. S., Secretary, Minutes of Chicago Meeting, 47. et oe THE AMERICAN MICROSCOPICAL SOCIETY ! 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Write for Catalogues and Prices The Kny-Scheerer Corporation of America Department of Natural Science 50-58 W. 23rd Street GeEAGAD ereND: New York, N.-Y. BIOLOGICAL SUPPLIES Michigan Biological Supply Co. Manufacturers of HIGH GRADE MICROSCOPIC SLIDES for ; BOTANY, ZOOLOGY, PHYSIOLOGY, HISTOLOGY, and AGRICULTURE We make a specialty of supplying slides to accompany Shull’s “Laboratory Directions in Principles of Animal Biology.” Cultures of Ameba proteus and other Protezoa Dealers in Preserved and Museum Material, Glassware, Lantern Slides, and Microtechnical Reagents All our supplies are guaranteed to be entirely satisfactory. Catalog sent on request. Nickels Arcade Ann Arbor, Mich. Members and Friends Will Find Our Advertisers Reliable THE AMERICAN MICROSCOPICAL SOCIETY Vv New Stereoscopic Eyepiece A most significant addition to our microscopical line, for both labora- tory and research workers ; has been enthusiastically received by those who have already seen it demon- strated. Presents following advan- tages: 1. Makes available the benefits of binocular vision at moderate GOSES 2. Can be adapted to almost any monocular microscope; 3. Gives stereoscopic effect ; 4. Parallel position of eyepiece tubes, adjustable for inter- pupillary distances, allows ui full relaxation of ocular PRICE, with Pair of Matched Eye- muscles, with consequent re- pieces, Evepiece Diaphragms and seule 3 Adapter for FFS Microscope, $50.00. licf from eve fatigue. Allowing the natural use of both eyes, this apparatus will be particularly appreciated by all those who are obliged to do frequent or extended work with the microscope. Write for illustrated, descriptive circular Bausch €§ lomb Optical ©. 502 St. Paul St., Rochester, N. Y. New York Chicago Washington San Francisco London Makers of Photographic Lenses, Microscopes, Projection Apparatus (Balopticons), Ophthalmic Lenses and Instruments, Photomicro- graphic Apparatus, Range Finders and Gun Sights for Army and Navy, Searchlight Reflectors. Stereo-Prism Binocu- lars. Magnifiers and Other High-Grade Optical Products. Members and Friends Will Find Our Advertisers Reliable THE AMERICAN MICROSCOPICAL SOCIETY Leitz Microscopes are the Standard of the World LEITZ “MON-OBJECTIVE BINOCULAR” MICROSCOPE The Modern Research Type This Binocular Microscope can be used with any of the standard objectives from lowest to highest power. This model originates with Leitz and was success- fully introduced in 1913. Other firms have copied this model but the individual design, superior workmanship and efficiency of the Leitz pattern will fully protect the prestige for the original type. Points of Merit 1. Binocular vision. 2. Perfect accommodation to any interpupillary distance. 9 Adjustment for any difference in refraction between the EVes. ts Complete elimination of eye strain. >. Improved quality of image. > Parallelseyepieces: 7. The possibility of using any favored objective from, the lowest power to the highest oil immersion. 8. Reduction in numerical aper- ture. — ELEITZ WerZba* Write for Pamphlet No. 1003 A OPTICAL ano” MECHANICAL NEw : ORK \ SURPASSED “oa EQUALLED Nea WORKMANSHIP RY. iris “SUPREME 60 East JOUStr Members and Friends Will Find Our Advertisers Reliable THE AMERICAN MICROSCOPICAL SOCIETY Vil THE SILVERMAN ILLUMINATOR offers important advantages for practically every application of the Microscope: a—It shows more detail. b—A clearer and better defined picture is presented to the eye and the camera. c—Several novel methods of illumination can be provided. d—It saves much valuable time. e—It prevents eye strain, eye fatigue and brain fag. f—It can be lowered into deep hollow objects. g—It gives excellent results for very low power work as well as higher magnifications, also in oil immersion work. h—It can be used with any microscope, ordinary or binocular. A small circular tube lamp surrounds the objective and fur- nishes a diffused and uniform illumination directly where it is needed. The Silverman Iliuminator marks A GREAT ADVANCE in Microscope Illumination WRITE FOR BULLETIN 45-C LUDWIG HOMMEL & CO. 530-534 Fernando St. ELECTRIC DARK FIELD ILLUMINATOR (U. S. Army Medical School Type) A Combined Dark Field liluminator and Microscope Lamp It Fits the Substage Ring of All Standard Makes of Microscopes It Is New, Original, Unique, Compact, More Efficient ANOTHER FORWARD STEP IN MICROSCOPE CON- STRUCTION. ANOTHER SPENCER TRIUMPH Pittsburgh, Pa. Send for Booklet SPENCER LENS COMPANY Manufacturers MICROSCOPES, MICROTOMES, DELINEASCOPES BUFFALO, N. Y. SPENCER BUFFALO [eurcac] SPENCER BUFFALO a Members and Friends Will Find Our Advertisers Reliable VIII THE AMERICAN MICROSCOPICAL SOCIETY Watson's Apparatus for Microscopes Watson’s manufacture a series of Achromatic Objectives of high and low aperture, and of varying powers, enabling the maximum effect to be obtained with every description of Object Glass. They correspond in correction and workmanship with Objectives of similar powers and apertures, and the high power Condensers can be made suitable for lower power Objectives by the removal of the top lens. THE HOLOSCOPIC OIL IMMERSION CON- DENSER. Power .22”, numerical aperture 1.35, the whole of which is aplanatic if used on the thickness of slip for which it is corrected. The finest Condenser obtainable for high power work. Optical part only, to fit the Royal Microscopical Society's Screw Thread, £9/12/6. Condenser Full ; ‘2 aero = | Diameter ser Anrtiipe Aplanatic Aperture Equivalent Focus of Back {AP Lens | Complete op Lens Complete lop Lens | Removed Removed Mac ro. Inch Ineh = Illuminator = ae = | 2 1225 Aplanatic = ; E d or; means ees ae -90 | 48 ily -66 = 5 I'he 1.0 95 40 4 1.0 77 Universal 3 Parachromatic 1.0 90 40 29 4 .62 WATSON’S HOLOS. IMMERSION PARABOLOID for the examination of Spirochetae, and the exhibition of ultra-microscopic particles, is the best high power Dark Ground Illuminator. Optical! Pantvonlw Priceres/11/6: Particulars of all the above, and of Watson’s Microscopes and Accessories of every description, are contained in their catalogue of Microscopes, which is published in 4 parts, as follows: Part 1: Students’ Instruments. Part 2: Research and Other Microscopes, and appliances of every description. Part 4: Instruments for Metallurgy, Petrology and Mineralogy. Part 5: Photo-Micrographic Apparatus and Accessories. Sent post free on request to: W. Watson ¢& Sons, Limited Established 1837 313, High Holborn, LONDON, ENGLAND Members and Friends Will Find Our Advertisers Reliable SA fh ea Wie Ti BAA i P a ery Beh st) ia QH American Microscopical 201 Society A3 Transactions Vv. 39-40 cop.2 Biological & Medical Serials PLEASE DO NOT REMOVE CARDS OR SLIPS FROM THIS POCKET UNIVERSITY OF TORONTO LIBRARY a me PY AOE STOR AGI if ‘eaiz: tease! ati etat (hy Bincky Apne ne atta caingn: Ve memeson , d rt ‘ 7 : Sa ety maretunenen rade seys f Re Fm Am 8 : Lee biAl be 34 he coed Pasa Mice mn er eh eee eR aha" yatine te oe,