bl ra ya ae ea = - = ee i ae —_——< ? ¥ —ia? ‘» De ao fy eS ae a as , on * => Mie toate ale POUR N AL OF MORPHOLOGY. EDITED BY C. O. WHITMAN, University of Chicago. WITH THE CO-OPERATION OF EDWARD PHELPS ALLIS, Penk aL LIE, Milwaukee. University of Chicago. HOWARD AYERS, T. H. MORGAN, University of Cincinnati. Bryn Mawr College. E. G. CONKLIN, E. B. WILSON, University of Pennsylvania. Columbia University. Vor SC VIE. BOSTON, U.S.A.: GINN & COMPANY. IQOT. Si ae 2 —) os, 4 - 7 i as 0 _ on 7 | ad 7 0} ooh Rides ia | a i" ' 7 5 et) oe ms eas 7 7 ft : nee vy ‘ = : Lg u rs a) Me > 4 me} . 2 iz} 7 i 7 7 - i : 7 7 a 7 owen, ; oa Phi fre ? a — ‘ FF Lp = Ms. ras : Volume XVII. September, 1900. No. f. JOURNAL OF VOT Ol OGY THE SPERMATOGENESIS OF BATRACHOSEPS. PoLYMORPHOUS SPERMATOGONIA, AUXOCYTES, AND SPERMATOCYTES. GUSTAV EISEN, Pu.D. TABLE OF CONTENTS. « PAGE BTINTRO DOCTOR Ys cer erie re seen as ONE Res oh 3 Pe VERTHODS (OW TN VRSTIGATION Ge 1 eel eo re ee ee eee te. SINT 4 EAE VCS Serer eres ed eee ee Nig te rege hares eur BYTE 4 5 Fa RS RAE ARES Th YU eee oe esa Agee | 0b Aen ee 5 Optical Methods and ‘Appliances, 2308 et a 7 DMPC ONSEUTUENTS WOR REVO AC Yonge Shee Vo al ye ae Ee) 8 Remrral Plepessoms) of Cel Sirsiciuves:.- 1s 8 JES SEDS Pe is OR SRSA ote ES nie ec Le eS ee 8 LEER TPR E TE By SOU STE LD ri aR Eee Ne a AL A eI a ee 9 Archosome or Centrosomal Structures.........2.......::0c0sscsseseeeeeseeeeeeesee fe) CFE ASOTCE ree nen RRR ee es eek te Leer tel ee Led fone Ct LR 9 Qy) LE SESE We 2 So Ngoc Ra SAS ES LD ce a 9 Bee SoS 8 HALE LA 2a 8 o8 ie ed fe) Plasmosphere, Granosphere, and Hyalosphere. Meves’sIdioplasm 10 ae Paar Pp our ee er hE de el eee 13 Cytoplasmic Membrane or False Nuclear Membrane. Cell Wall... 15 LEE CELE Do So? RS aA Ee OS eee eee ee 16 PO i ai at, nc gO CUE ee Ee Ciel De eR 17 ACETIET ETI ATG PI eels ae ane be eed di dh, 17 2 EISEN. [VoL. XVII. PAGE GChromioles.icicesi ies cca ee cca hecc st pastes epee eatsnetsoever cnet 18 Chromoplasm .........-------c--c--c--eceececeesecsseececeeceecnsenenen sencereneoscsnasassuscsosearad 22 Chromomeres .........- » ASO Ra EE Sa e202 SL oth tee ea eenuer erane een ces eanaren 23 DOs Va (hfe ere eae eee sreee ce ectootee cecteu copenase roster noha hae bkecaathtaer tne eneicensene 25 ChrOMOSOMES: highs sssee ee eee dca ce teeta oa ae ree ote ae 26 Chromoplasts and Endochromatic Granules ..........0--ss1-sesceeseeceeeeees 28 Tene avoyenteyg (8 Cyber octecectccr cosenecdacoresoceen a ocebtaroccecnbacuaece 34 Linoplasts or Drie Necleola or orc cc cer ecc eases nares a2 Sacer pe ee ees 34 1 DFE esses hee eee enmeete eee dap cee occ ocece ccc anos eee Soccaccec sc cuecesacLROSE 35 Nae aur ile roa xen aie eeee sae ease aeons 37 Phylogeny of the Nucleus <2... -2.2--00.-ccs-scencte-ansereonemsnnennnnnnpsorestensnsstnse 38 AP CHOS OT70E: 2 ssste nts ee eR ee ote aaa cee aera sane eee eer cee 39 The Archosome Proper: Its Structure, Centrosphere, Somo- Sphere, Quid Meme Gl sprees te eee ce eee acee cece ea ece tesa eee 39 Accessory Archosomes, their Structure and Functions. Expul- sion of the Superfluous Accessory Archosomes ............::::s:e000e+ 43 TVi0 SBINDLES (AND MS BINDDID i HINBIGRIS iene seeceteneete cer ents eastern eee cae cree eee 45 General: Remankesyer ee oo aA a eee eee eae 2d eee re ease 45 Mantle Fibers, Polar Fibers, and Central-Spindle Fibers ................ 45 Contractile: Fibers is osc es ee eg a ae ere eno an sartc a arcu coaor omer en 48 Fiber Cones and Retractile Fibers of the Spindle Cones................ 49 Spindle bxidge and | Mid-Day oer oe ce arene cee eee eee reer 51 A PNR Go TAS) Tol IRU TIAN E) (CHOTIUS ohh oe ot oeneme doce st sce ep ob enoo coer eo uS RoE ase eEo oe 52 Polymotphous Sperimato ronal so: ecescecete cree sect tent etarerneeen Perera 52 PATEK OC YES Peas ace e me ce sr eee ee 56 SpermatoCytes oo iciceiitctenk ceecestsacasoe seascaetiten suet eancee oe eRe nese rear ner 59 Sperinatids 2.1170) 1 Ee eae ee ecco eene a Seer ee eenat ee aceae ca 60 WIT; IMEPTOSIS ecdee sce Sl ic AR a Toe ae ae eee ER Se ae 60 A General Review of Mitosis. The Two Parallel and Inde- pendent Processes of Evolution and Development: The Radiosomic and) the (Chromosome yess ee eee nen 60 The Radiosomic Process, or the Evolution of the Spheres, the Spindle, the Fibers, and the Formation of the Cell Wall............ 63 The Chromosomic Process, or the Evolution of the Chromioles and their Formation into Chromomeres and Chromosomes...... 67 Equations or (Reduction. css sere es eee eee eee 76 Falungey Stages inthe Mitosis sss vest eee eee 76 Villars sTRUCLURES (OFLTHE) PROTO PHASMase oe eee i) ibers:¢Granula-andwAliveolesenc eee eee ee 77 VIII. PERMANENCY OF THE COMPOSITE STRUCTURES OF THE CELL........ 82 STEXG HS UMN R Vie ohare niet) etd OE che une nee 84 XIN OMEN CLAM URI Selec rites Se cuceelagsacet tn sates secensceedececoe taeda ee 90 Des IT URRAT URC ae tases estectes ever ofaNiae sti pec teeaees oo cubeccesadstt gens ioe yee 97 XMS EXPLANATION VON LPH E PP TGU RWS ee) eoeern ony eee) aoe eee 100 XIII. STAINS, FIXATIVES, AND OPTICAL APPARATUG........--.cccssscoosssccsleecenseees 117 Nort. SPERMATOGENESIS OF BATRACHOSEPS. 3 I. INTRODUCTORY. OwinG to a projected and extended voyage, this paper had to be brought to a sudden close, and much which I had in- tended to include in it had to be left out and deferred to a second part. This latter half will include the somatic mitosis of the polymorphous spermatogonia, the evolutions of the spermatids and their development into spermatozoa, and also a discussion of the literature. In this paper I have merely endeavored plainly and briefly to describe my own investiga- tions, and time has hardly permitted me even to touch upon those made by others on the same subject. The results of the present investigations, of whatever value they may be, are principally due to improved cytological and optical methods, especially to the new fixatives and to the achromatic light, all described in their proper places. With- out them the chromioles would yet have remained a mystery, at least as far as my own investigations are concerned. The figures illustrating this paper have been corrected as many as four different times, and the first thirty figures made have been completely redrawn, in order to secure that accuracy of detail which can only be had after repeated failures. It is proper to state here that the testes of Batrachoseps are very favorable for study, being small and containing large cells. But these advantages are more than offset by the scarcity of the material. While these batrachians are very common almost everywhere in California, their testes are only active at a time when it is almost impossible to procure any specimens of the species. Batrachoseps attenuatus is only adult in the months of June and July, at a time when, on account of the dry season, these animals have retired down in the ground, almost out of reach. In the summer of 1897 I had, however, the good fortune to find in the end of June three fully adult specimens at Monterey, Cal., in a damp meadow which had been kept cool by the fogs from the ocean and shaded by overhanging trees. The largest of the three specimens was made useless by an accident in sectioning the testes; the others, however, turned out most admirable preparations, 4 EISEN. [VoL. XVII. which were made the material for this memoir. After- wards I was of course able to supplement them with less favorable material from specimens collected at other times. In size the adult testis is about five millimeters long by one millimeter wide. It consists of only one single lobe, undivided and of cylindrical shape. In the central parts of this lobe are the ripe spermatozoa, while the other cells are found arranged on either side in the direction of the long diameter of the testis. The four testes were sectioned longitudinally, thus affording a comprehensive view of the arrangement of the different cells. It is with much pleasure that I here acknowledge my indebt- edness to my esteemed friend, Dr. W. J. V. Osterhout, of the University of California, for many valuable suggestions and for assistance in correcting MS. and proof. II. Metuops oF INVESTIGATION. Fixatives. The first investigations were made on testes fixed with the classical fixatives—Flemming’s chromo-aceto-osmic mixture and the platino-aceto-osmic mixture of Hermann, used in various strengths, with or without admixture of water. Heidenhain’s corrosive-sublimate-acetic was also tried, both with and with- out addition of formalin. Experiments were also made with a number of other fixatives, such as mixtures of Flemming’s and Hermann’s with corrosive-sublimate and palladium-chloride. Vanadium-chloride, uranium-chloride, and osmium-chloride were also experimented with, all of which, with the exception of the last, proved of no value. I soon satisfied myself that any mix- ture containing either platinum-chloride or osmic acid, or both, would completely ruin several of the outer rows of cells, mak- ing them unfit for microscopic research. As the testes of Batrachoseps are so very small and possess only a few rows of cells, none of the above-mentioned fixatives could thus be used. Platinum-chloride is even more injurious than osmic acid ; while the latter destroys the chromatin, the former ruins the finer structure of the cytoplasm. Although by the employment of No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 5 these fixatives some of the interiorly situated cells gave fairly good images, yet it was readily seen that the cytoplasm of the cell had become greatly contracted and distorted, to such an extent as to represent no more the true structure of the cell. It is comparatively easy to fix chromosomes and spindles, more difficult to fix the cytoplasm and the linin. Osmium-chloride is in many respects a most valuable fixative, especially in solu- tions of from one-half to one-tenth per cent, but it always pos- sesses the undesirable quality of blackening the tissue, though in a lesser degree than osmic acid. I have, however, no doubt that this chemical will be found very useful for fixing several kinds of tissue, especially in connection with potassium- bichromate, when it allows of intense staining and detailed differentiation. The fixative on which I finally decided as giving the most satisfactory results, as regards the fixation of the testes of Batrachoseps, is a mixture of iridium-chloride- acetic, according to the formula published in the Zeztschrift f. wiss. Mikr., Bd. XIV, pp. 195-202. The time of fixation is from three to twelve hours, though I think that the best results were had with the shorter time. There is no percep- tible shrinkage of the tissue, no blackening of the cells, and the outer rows of cells are as perfectly fixed as those in the center. After fixation the testes were washed in tap water for about one hour, then passed through thealcohols. For clearing, ber- gamot oil was found most suitable, but it was followed by xylol, which latter was again displaced by bergamot before imbed- ding in paraffin. The sections were cut in paraffin of 54 Fahr. melting point, and from 4 to 6 thick, each cell being cut in from two to three parts. This latter is of importance because cells which are not cut into do not stain properly, making it impossible to study the finer structures of the cell. The sections were then fixed to the slide by the alcohol method as described in Bd. XIV, Zeztschr. f. wiss. Mikr. (1897), pp. 195-202. Stains. The majority of the sections were stained by the Benda iron- haematoxylin method, and after-stained with congo. Another 6 EISEN. [VoL. XVII. set was stained with congo, thionin, and ruthenium red, as will be described below. The liquor-ferri-sulphurici-oxidati was used diluted about six times, and the slides were kept in the solution for about twenty- four hours. The haematoxylin solution was used concentrated and contained about 10% of alcohol, the solution being a year old. The sections were kept in the haematoxylin solution for from forty-eight to seventy-two hours, the longer time giving the best results. The differentiation was made with a 10% solution of glacial acetic acid in water, to which was added a small part of the liquor-ferri, sufficient to give it a very pale straw color. In from fifteen to twenty minutes the differentia- tion was finished. The slides were now rinsed in water and counter-stained with a watery solution of congo for one or two minutes, then as quickly as possible dehydrated in absolute alcohol, cleared with bergamot oil, and mounted in gum-thus in xylol. Several of the slides were stained over two and even three times before a sufficiently satisfactory differentiation was obtained. The use of congo as a counter-stain was decided on only after long experiments with numerous other anilin colors, and it proved to be the only stain which gave the desired differentiation in the highest degree. It was the only satis- factory stain for the differentiation of the spheres and their secretions. Another combination of stains which proved useful is a triple stain of congo, thionin, and ruthenium red. The slides were first stained for a few seconds with a weak solution of congo in water, then for about ten minutes with thionin in water, and then differentiated with a watery solution of ruthenium red. This latter stain was made extremely weak and of a pale rosy tint ; still the differentiation was accomplished in a few minutes. The ruthenium washes out the thionin, and the differentiation should always be carefully watched under the microscope. This combination of stains proved especially useful for differ- entiating the chromoplasts, and also for the study of the out- lines of the chromosomes, especially where the latter overlapped each other, as the outlines of the separate chromosomes could always be distinctly seen. No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 7 Optical Methods and Appliances. No one who has not used an oil-immersion substage con- denser can have any adequate idea of the value of such an appliance. In the study of the finer structures of the cell it is of equal importance with the apochromatic objective, and its value cannot be overestimated. It is my opinion that a correct and proper view of the structure of the protoplasm cannot be had without the oil-immersion condenser, and that opinions based on observations made without this condenser must neces- sarily need to be reconsidered. An achromatic, or better yet an apochromatic, condenser should be used, and the immersion oil should be slightly denser than the oil used on the objective, in order to counteract the thickness of the slide. This can readily be accomplished by warming the oil for a short time, or by using oil that has become thicker from ordinary exposure to the air. The oil-immersion condenser increases the sharp- ness of the image and brings out details not otherwise visible. The images were studied with artificial light alone, a filter of cyanin and methylene blue being interposed between the Welsbach incandescent gas burner and the substage condenser. For a more detailed account of this light see Zeztschr. f. wiss. Mikr., Bd. XIV, pp. 444-447, 1897. The use of this light enables us to work continuously, independent of sun and clouds, day or night, with the same strength of light and with the same facility. This light has also a great advantage in not injuring the eyes, not even tiring them perceptibly after ordinary work. The light has also another advantage in that it differentiates structures which are not differentiated by stain- ing. For instance, by the daylight and after staining with congo no differentiation was had between the linin granula and the cytoplasmic granula, but with the artificial light the linin gran- ula were seen to be of a gray or brown color, while the cytoplasmic granula were stained palered. A better image can be had with this artificial light than with the best white-cloud light, and the image is also perfectly steady, which it never is with even the best cloud light. The sections were studied with Zeiss Apochromats, 3 mm., Ap. 1, 40, and 2 mm., Ap. I, 40; Oc. 12 and 18. 8 EISEN. [VoL. XVII. III. CoNnsTITUENTS OF THE CELL. General Divisions of Cell Structures. The division of the cell structures adopted in this paper is almost the same as the one proposed in my paper on the plas- mocytes of Batrachoseps, the only important change being that of the word centrosome to centriole. The principal rea- son for this change is that many investigators have not only used this word for different structures, but in some instances have even discarded it altogether. The confusion is really so great that it is in many instances impossible to know with cer- tainty what organ or what part of the cell is referred to. W. Flemming, in his report, “‘ Morphologie der Zelle,” 1897, rejects the name centrosome and substitutes the word ‘“Centralkorper.”’ As this word cannot possibly be accepted by other investiga- tors than Germans, and as Boveri has previously named this body the centriole, I can see no valid reason why we should drop’a really very useful word, about the meaning of which there cannot be any misunderstanding, and which is so con- structed that it can be adopted in every language used by biol- ogists. Literal translations of new words often so conflict with words already existing that great confusion results. It seems, therefore, most appropriate that in composing new words they should be so constructed that they may with a slight change be used in other languages, or, better yet, be used without any change. Words of this kind are, of course, words of Greek and Latin derivation. I would also suggest that every biologi- cal paper be accompanied by definitions of the nomenclature, worded in such a manner that no misunderstanding will ensue. If such a method had been adopted, we would not now have had years’ wrangling about, for instance, the single little word “‘centrosome.” In this paper I propose to use the following nomenclature for the divisions of the cell: Cytosome — the purely cellular part of the cell, the cytoplasmic parts, all parts exterior to the nucleus, except those bodies which are known as archosomes or parts belonging tothem. The cyto- No, 1.) SPERMATOGENESIS OF BATRACHOSEPS. 9 some thus contains such constituents as cell wall, cytomicro- somes, the two spheres which I here designate as granosphere and plasmosphere, metaplasmic secretions and metaplasmic granules, various rays and fibers, and spindles. Karyosome, or nucleus — comprises the following parts: nuclear wall, or karyotheca, chromosomes and their constitu- ents, linin, what is generally known as nucleoli of various kinds. All bodies which when the cell is at rest reside within the nuclear membrane. Archosome — the centriole with its spheres, the somosphere and the centrosphere, all structures which may be counted as centrosomal structures. When there are more than two archosomes, I refer to the others as accessory archosomes. For the innermost dark-staining granules I have adopted Boveri’s name, ‘“centriole.’”’ The thin zone surrounding the centriole or centrioles is the somosphere, and the zone sur- rounding the somosphere is the centrosphere. The archo- somes or archosomal structures have not with certainty been found in the higher plants. The Cytosome. By the cytosome I understand all that part of the cell which is situated exterior to the nucleus, excepting those parts which are undoubtedly of the same nature as the archosomes. The cytosome comprises thus the following parts: the cytoplasm proper, the plasmosphere, the hyalosphere, the granosphere, metaplasmic secretions, the cell wall, and finally some granules of undetermined nature, generally scattered among the cytomi- crosomes, also the fibers, the spindle, and the mid-body. The Cytoplasm. — During the greater part of the life history of the cell the cytoplasm proper is difficult to distinguish from the various granules comprising the spheres. Sometimes it is also difficult to distinguish it from the linin granules of the nucleus. The latter difficulty exists only when the nuclear membrane has been dissolved, as at that time the linin gran- ules are scattered all through the cytoplasmic part of the cell. But even then the cytoplasmic granules may be distinguished from the linin granules both by their staining quality and by 10 EISEN. [Vo. XVII. the way they are arranged into threads or fibers. With the light-filter the linin granules appear darker than the pure cytoplasmic granules, and it is even possible under favorable circumstances to follow the course of the linin granules from their dispersion from the nucleus to their appearance in the cytoplasm. While I have included the two spheres as a part of the cyto- plasm, I nevertheless hold that they are of a somewhat different nature, with different functions, from the cytoplasm proper. During the perfect resting stage of the large cell with poly- morphous nucleus the cytoplasm proper is confined to a very thin stratum surrounding the deeply folded nucleus. At that time there is no distinction between the granules of the cyto- plasm proper and the granules of the spheres (Fig. 1), and it appears as if the latter might later on be differentiated out of the former, though we can with equal reason assume that they are fundamentally different, but that they are intermixed, and that they cannot be distinguished one from the other. At a later period in the development of the cell such a distinction is possible, as the staining capacity is much greater in the granules of the spheres than in those of the cytoplasm proper (Figs. 30, 58, 60). During this early resting stage of the polymorphous cell the cytoplasm is never accumulated close to the cell wall, but merely forms a very thin zone around the nucleus (Fig. 1). As the cell grows, this zone increases in size and soon fills up all the available space between the nucleus and the cell wall, though it is always denser in the immediate vicinity of the nucleus (Figs. 3, 10, 12, 15, etc.). In the early stages of this class of cells the cytoplasm proper as well as the primitive spheres are composed principally of granules, but at a later stage, when the spheres are formed, the cytoplasm proper is generally distinguished by a fibrillar structure, while the spheres are almost exclusively granular (Figs. 34-37). The Spheres. By the spheres I understand that denser accumulation of cytoplasmic substance variously designated as spheres, archo- INO. T.] SPERMATOGENESIS OF BATRACHOSEPS. Et plasm, aster, etc., generally containing the archosomes. The spheres when perfect are differentiated into an inner and an outer sphere, and at times also the outer sphere is further dif- ferentiated into two distinct zones (Figs. 8, 9, etc.). The word “differentiated’”’ is used in the same sense as separated and is not intended to indicate that the two spheres are differen- tiated from the same kind of protoplasm. The inner one of the spheres is the most distinct and also the most permanent of the two. It is more constant as to form, and is characterized by a capacity to stain much deeper than any part of the outer sphere. It is also during a part of its life cycle well defined, having then the form of a concave disc, or a mulberry-shaped body, one side of which is strongly concave, while the other is more or less noticeably convex (Figs. 12, 29-31). There is reason to believe that this inner sphere is always concave, but that the concavity of the sphere is only perceived when the sphere is seen from the side (Fig. 12), the con- cavity not being visible when viewed in the other direction. The comparison to a mulberry is yet more justified by the structure of the sphere. It is, when perfect, always composed of a number of alveoles of almost equal size, and so arranged that the wall of the sphere is just one alveole thick. The cav- ity of the sphere is not an empty cavity, but is more or less densely filled with granules, less distinctly arranged in alveoles. At a certain stage in the activity of the sphere and the archo- some this inner more loosely constructed part of the sphere is drawn out, the archosome being at its top, forming a pointed cone of less staining capacity (Figs. 28, 35-37). The alve- oles are non-permanent structures and formed by the peculiar arrangement of the granules composing the spheres. It ap- pears as if these granules secreted some distinct substance, and that this substance was held together by the closely ap- proached granules themselves, thus forming a bladder-like alve- ole surrounded by a membrane of granules. The development of the spheres will be described in another place; here it will suffice to state that the inner sphere is during mitosis gradu- ally dispersed, part of it being undoubtedly used up in the for- mation of the central spindle. Similarly the outer sphere is 12 EISEN. [Vo. XVII. dispersed at an even earlier stage, the secretions of its gran- ules, or perhaps even the granules themselves, supplying mate- rial for the new membrane which is formed between the two daughter-cells. In a paper on the plasmocytes of Batrachoseps I have de- scribed and designated the spheres of the erythrocytes as gran- osphere, hyalosphere, and plasmosphere, these three spheres being of strictly cytoplasmic nature. A comparison with the spheres of our present cells satisfies me that the inner sphere is identical with the granosphere. For the outer sphere I use the name plasmosphere, though it is not absolutely settled to my satisfaction that they are in every way identical. But the similarity is considerable, even to the extent that we find be- tween the plasmosphere and the granosphere at times another zone which probably is identical with the hyalosphere (Figs. 8, 16, 17, 34). In this paper I will, therefore, refer to the two spheres as the plasmosphere and the granosphere. While in the plasmocyte the non-staining sphere surrounding the grano- sphere has the form of a narrow, even band, the non-staining zone in our present cells is frequently aster-like, radiating through the plasmosphere (Figs. 6-8, 14). The three spheres during all their different stages of evolution possess a granu- lated alveolar structure, the cytoplasm proper taking the form of frequently granulated fibrilla, especially nearest the cell wall. When I had almost finished this paper I found that Meves has proposed the name “idiozom”’ for the two spheres, or, as he defines it, “for the specific covering which surrounds the Centralkérper in the testes cells.’ The word is apparently selected under the supposition that the spheres are especially intended for the Centralkérper. That such is not the case I expect to show in this paper. Moreover, the new word does not distinguish between the two spheres, which, as I expect to demonstrate, are distinct and independent structures. If we are to retain one name for the two spheres, then the word ‘“‘archoplasm’”’ seems to me as good as any other. Neither of the two words expresses the true nature of the bodies which they are intended to designate. The names which I propose to No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 13 retain in this paper have the advantage of distinguishing between the two spheres, and have besides the priority. Upon the value of the latter I shall, however, not insist, and I am willing at any time to discard any words introduced by me or by any one else as soon as better ones are found, but not until then. Position of the Spheres. As will be seen from a perusal of Figs. 10-17, the spheres are only situated on the cell axis when they are in a stage of comparative rest, and at a time when the spheres and the nucleus appear to balance each other. If, on the other hand, we examine such figures as 42 and 45, we find that the spheres, especially the granosphere, have a different position relative to the central spindle and the nucleus. Instead of being situated on a line passing through both the central spin- dle and the nucleus, we find them situated ona line passing through the equator of the central spindle. From this we can formulate a rule that the position of the granosphere during the radiosomic process is dependent upon the position of the central spindle; and vice versa, that the position of the central spindle is dependent upon that of the granosphere.. Whatever be the relative position of the nucleus on one side, and the granosphere and the central spindle on the other side, the cen- tral spindle will always be so situated that a line passing through its equator will also pass through the granosphere. The object of this relative position of spheres and central spindle is undoubtedly to enable the two opposite poles of the central spindle to draw an equal amount of nourishment or material from the granosphere. As regards the mutual position of the two spheres, I expect to show that they are not directly dependent on each other, and that the position of the granosphere inside of the plasmo- sphere is probably regulated by convenience more than by dependence. If the granosphere were situated anywhere else it would not be able to furnish the central spindle with the material required for its development. The plasmosphere again, which furnishes material for the mantle fibers and for the new cell wall, must of a necessity be on the outside, in 14 EISEN. [VoL. XVII. order to be able to assume its proper position near the equa- tor of the cell, where it is most required. Again, the develop- ment and the evolution of the cell require that as much as possible the various parts should be arranged concentrically. Metaplasmic Secretions.— These secretions can be readily distinguished from the permanent elements of the cell by proper methods of staining. Among the methods which I have used there are only two which have proven of value. One is the Flemming triple stain, the other is the iron-haema- toxylin stain, with an after-staining with congo. The latter method is much preferable, and it may almost be considered as a specific stain for the secretions from the spheres. It has already been stated that the ultimate visible structure of the spheres consists of granules and that they are arranged around alveoles. It is these alveoles which contain the metaplasmic secretions, and the only way to explain their presence is to assume that they are secreted from the granula of which the spheres are composed. The secretions appear only in the alveoles, and when these are scattered during mitosis they carry the secretions with them. Even with the highest op- tical powers no structure can be perceived in the secretion. During the metaphase the alveoles, together with their secre- tions, are found in the vicinity of the equator where the new cell membrane is to be formed. The secretions from the granosphere, and perhaps some of its granules, are used up in the formation of the central spindle. At least the granules lose, at this time, their intense staining capacity, diminish in size, and cannot be followed any longer with any certainty. Fibers and rays, both from the central spindle and from the spindle cones, are frequently found ending in alveoles filled with metaplasmic secretions, as if they were receiving nourish- ment from them (Figs. 41, 42, 45, 61). The metaplasmic secretions teach us, among other things, that the two spheres are structures independent of each other, that one sphere is not a modification of, or a secretion from, the other, but that each is of a distinct nature. When the spheres reconstitute they do not do so together, but often in different places of the cell, later on to be joined together. INO= 1:]] SPERMATOGENESIS OF BATRACHOSEPS. 15 Cytoplasmic Membrane and Cell Wall, — The cell wall is un- doubtedly the most constant structure of the cell. I have not made this structure the subject of any particular study and can only say that it appears to be composed of minute granules, closely approached to each other and evidently of the same nature as the granula composing the cytoplasm of the cyto- some. The formation of the new cell wall between the two new daughter-cells will be described under the general heading of mitosis. Here I will only mention that the new wall is formed by the aid of metaplasmic secretions from the outer sphere. All through the evolution of the cell we find that wherever large vacuoles are formed in the cell, these seem to become surrounded by athickercytoplasm or incipient membrane. This is, I think, especially the case when these vacuoles contain some substance differing in quality from that surrounding them, in which instances the cytoplasm appears to thicken into a veritable membrane, greatly resembling a thin cell wall. At a certain stage in the mitosis of the cell, when in the end of the anaphase the new nucleus is beginning to increase in size, a new membrane is formed surrounding the nucleus, but at a considerable distance from it. This membrane is not a nuclear membrane, but a true cytoplasmic membrane, which is again dissolved, as soon as the new nucleus has reached its final or desired size. This membrane only serves as an attach- ment for the cone fibers, and by being pulled outwards causes a large vacuole to be formed around the nucleus, thus giving the nucleus ample room to expand and to grow (Figs. 59-68, also Fig. 70). The nuclear membrane is formed later, imme- diately around the chromosomes, often while the cytoplasmic membrane is still in existence, as, for instance, in Fig. 7o. Later on this cytoplasmic membrane is dissolved. The process of the formation of this false nuclear membrane, as well as of the inner and thinner membranes around the vacuoles, and of the cell wall itself, is, I think, one and the same, a condensing of the cytoplasmic granules. In the formation of the new cell wall the draught on the cytoplasm is so great that an extra supply of cytoplasm and nutriment is required, which supply is furnished by the plasmosphere and its metaplasmic secretions. 16 EISEN, [VoL. XVII. Paracellular Bodies. —1 designate as paracellular bodies numerous non-cellular bodies situated between the regular cells of the testes. They appear to have been expelled from the cells. Some of these bodies are lying free in the intercellular space, others are more or less closely attached to the exterior surface of the cells. These bodies are rarely found among the polymorphous spermatogonia, or among the auxocytes, but are quite numerous among the spermatocytes, the spermatids, and the spermatozoa. At times we find only a few, at other times we find them by hundreds. They may be divided in two classes, one consisting of bodies of somewhat larger size and which contain no granules. The other class comprises bodies of smaller size, but which contain one or more darkly stainable granules. The larger of these bodies are frequently attached to the cells by thin threads (Figs. 67, 109). The smaller ones, containing the granules, are sometimes attached, but more fre- quently free (Figs. 85, 88). As regards the interior structure of these bodies we find that those without any granules present a striated appearance, as if their interior consisted of a fine network. By the use of the congo-thionin-ruthenium method these fibers can be stained bluish, while the other parts re- main red. } The structure of the smaller bodies with the granules is quite different. There is no sign of any fibrillar structures nor of any network, but they are seen to contain from one to five dark-staining granules, mostly arranged along the sides of the wall of the main body. These bodies vary very consider- ably in size, some being many times larger than the others. If we consider the origin of these bodies, large or small, there seems to be only one theory that is plausible, that they are bodies expelled from the cells. A perusal of the figures re- ferred to above makes this supposition also probable. We see on the surface of many cells bodies exactly similar to those which are free; at the same time we find in the interior of the same cells bodies of a similar appearance. From my observa- tions I judge that the bodies with the granules are expelled accessory archosomes, while those without granules are ex- pelled fragments of the spheres. The increase in size can be NG; i) SPERMATOGENESIS OF BATRACHOSEPS. L7 due to a swelling up of the bodies as soon as they enter the intercellular liquid. Bodies of both kinds accumulate often in very large masses between the cells and are often found in complete dissolution. In another place I have suggested that the expulsion of the centrosomes is affected when there are too many archosomes in the cell, more than are necessary to accomplish the mitosis of the cell. Karyosome or Nucleus. General Remarks.— The constituents of the nucleus may, in a general way, be divided into three parts: vzz., chromatin, linin, and nuclear wall. But as the nuclear wall is probably only a thickening of the linin, just as the cellular wall is only a thickening of the cytoplasm, we may dispense with the third division and simply divide the nucleus in two distinct parts, chromatin and linin. In this general division we must include under chromatin such bodies as the chromoplast, directly to be described, while under linin we must arrange the other class of nucleoli, the linoplast, also to be further described below. But while it seems that the true nucleoli or linoplasts are principally of importance in furnishing or regulating the sup- ply of linin, I must concede to the chromoplast a much more important function, that of regulating the formation of the chromosomes. It seems to me probable that the chromoplast has the same function to perform inside the nucleus as the archosome outside of the nucleus, and that while the archosome regulates the radiosomic process or the formation of the spindle and the final separation of the chromosomes, the chromoplast regulates the chromosomic process inside the nucleus. The following elements of the nucleus are distinguished and will be described more in detail below: chromioles, chro- momeres, chromosomes, endochromatic granula, parachromatic granula, chromoplast, chromoplasm, linin, linoplast, and nuclear membrane. These constituents are not of equal value and importance. The chromioles, the chromoplast, and the linin granula are the most permanent elements of the nucleus. All the other constituents of the nucleus, such as chromosomes, chromomeres, and linoplasts are only temporary and not 18 ; EISEN. [Vou. XVII. permanent organizations. As regards the nature of the para- chromatic granules we do not know anything with certainty, but it seems probable that they are of great importance. The Chromioles.— The chromioles are the smallest visible organized parts of the chromosomes. They undoubtedly con- stitute the most important parts of the chromosomes, the fun- damental elements which the other parts of the chromosomes only serve to nourish and to preserve. If we view a perfectly fixed and stained chromosome during any of the mitotic phases, we find that it is not a homogeneous body, but one that shows considerable differentiation in a regular manner. We first observe that the outline or margin of the chromosome is not an even one, but one which shows deep indentations of even size and number. These indentations are so arranged that the chromosome appears to be more or less beaded; that is, a convexity on one side corresponds to a convexity on the other side, and a concavity similarly corresponds to a concav- ity. We moreover find that these beads are of a constant num- ber, at least in chromosomes of average size. A chromosome of Batrachoseps in the beginning of the metaphase of an auxo- cyte contains just six such beads, the beads being identical with chromomeres. A closer study of one of these chromomeres shows that they are not of a homogeneous structure, but that each one of them contains several interior round granules, sur- rounded by an apparently homogeneous substance. These granules, for which I propose the name of chromioles, are of globular form and of equal size (Figs. 53, 54, I12, 120, etc.). I need not point out the necessity of having the chromosomes properly stained. If too dark, the chromioles will not be seen, but the whole chromosome will appear as a solid homogeneous mass of chromatin. Even when the chro- momeres have been so fused together that the margins of the chromosomes are only slightly wavy, the chromioles are yet distinct enough not only to be seen, but under favorable cir- cumstances to be actually counted. A very good view is had of the chromioles in the chromosomes, of which Fig. 112 gives as correct a representation as it was possible to make. Of course, instances where chromioles are as distinct as these No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. I9 are comparatively rare. In most instances they can only be counted here and there in the same chromosome, the trouble generally being that the chromosome has not been properly differentiated. But wherever glimpses of the chromioles are had it will be seen that they are arranged in rows, one row on either side of the chromomere, and parallel to the longer axis of the chromosome. As is to be expected in a case like this, where we view an object of so small a magnitude that it lies on the limit of vision, it is a most difficult matter to count the chromioles and to be sure that the count is correct. I have made a number of countings, almost wherever I found a suit- able opportunity, and the result is that I consider the number of chromioles constant in every chromosome of regular size. Thus in the metaphase-chromosome of the auxocytes and sper- matocytes there are three chromomeres in each prong, or six chromomeres in all, making six chromomeres for the whole chromosome. Each chromomere contains six chromioles, three at each margin, which makes thirty-six chromioles for the whole chromosome. The regularity of the chromioles, both as regards number, size, form, and arrangement, precludes the possibility of their being artefacts, and we have no alterna- tive but to assume that they are bodies of permanent structure and of the highest importance. The question now arises, to what extent can we trace the chromioles, backwards as well as forwards, in the development and evolution of the chromosome. This subject will be more particularly entered into when we discuss the development and evolution of the nucleus, and here it must suffice to give only a brief outline of the results of my observations. The chromioles can be readily observed in all the different stages through which the chromosomes pass, except in the confluent umbrella stage in which I have so far not been able to view them with any degree of satisfaction and clearness. In that stage there exist in the confluent mass besides the endochromatic bodies numerous dark staining gran- ules, but they are irregularly scattered and stain darker than the chromioles in other places. But while the persistence of the chromioles in this stage has not been satisfactorily demon- strated, it is at least highly probable, as immediately when the 20 ELSE WN. [VoL. XVII. chromosomes begin to reappear from the confluent umbrella, the chromioles appear at once and as well defined as ever. We therefore must assume either that during the confluent stage the chromioles do not stain sufficiently to be distinct one from the other or from the chromoplasm surrounding them, or that those globules which are observed there are actually the chro- mioles, though less regularly arranged. In all previous stages of chromosomic evolution the chromi- oles are distinct in almost every chromosome, and, as I have said, may in favorable instances be counted. Beginning with the resting stage of the nucleus of the polymorphous spermato- gonia, we find that the chromioles are the only parts of the chromosomes which are distinctly visible or regularly organ- ized. In this stage the chromioles are not united into chro- momeres and chromosomes, but occur free in the nucleus and separated from each other and only connected by a thread of linin. They do not even appear to be surrounded by the usual covering of chromoplasm, but are, so to say, strung one after the other on linin strings, which latter apparently run in the same general direction (Figs. 1-3). In a somewhat later stage several, or from two to three, chromioles are seen to congregate together and form the beginning of a chromomere, as, for instance, in Figs. 4, 5, etc. In a later stage the chromomeres are yet more dis- tinct and they are then seen each to contain three chromi- oles, situated very close together and surrounded by a thin film of lighter staining chromoplasm (Figs. 12-14). When again at a later stage the chromomeres have been perfectly formed, we find that each chromomere contains six chromioles and the supposition lies near at hand that each individual chromiole has divided in two (Fig. 15). The chromioles are now so arranged that three and three are on each side of the chromomere, there appearing between them a lighter staining line which may be followed all through the leader or spireme segment. When this segment splits in the next stage the splitting is carried along this line, and the newly split half will thus only possess three chromioles in each split chromomere. But when at a later stage the chromomeres have formed into No: 1] SPERMATOGENESIS OF BATRACHOSEPS. Bi their final number, then we find that each chromomere con- tains six chromioles, just as before (Figs. 24, 48, etc.). As the chromomeres fuse into each other, the chromioles also become correspondingly more closely set and finally they appear in the chromosome as two parallel strings imbedded in a common sheath of chromoplasm. This leads us up to the very point from which we started, the perfectly formed chromosome in the metaphase. We can, if we wish, follow this process - all through the evolution of the polymorphous spermatogonia, the auxocytes, the spermatocytes, and partly also into the sperma- tids, though the latter are so minute that their finer structure can be less satisfactorily studied. In order to test the existence of chromioles in chromosomes of other animals, I have fixed testes, by the iridium-chloride method, of a number of other animals, especially of insects, and I am thus able to state that in every instance where the chromosomes are of sufficient size to allow of a closer study, I have been able to demonstrate satisfactorily the existence of the chromioles. They are espe- cially well defined in species of orthoptera (Stenopelmatus). From the above observations I conclude that the chromioles are permanent structures in the chromosomes, and that they are the smallest visible individualized and organized parts of the chromosomes, and further that the chromoplasm, the chro- momeres, and the chromosomes are merely structures for the conveyance of, the nourishing of, and the partition of, the chromioles. There yet remains to say a few words about the division of the chromioles. The proper increase of the chromioles is, of course, an absolute necessity, provided we are correct in assum- ing them to be the most important parts of the nucleus. As the chromioles are too small to allow of any direct observation as regards multiplication, all speculations on this subject are as yet premature. The counting of the chromioles is a most diffi- cult matter, as not even under the most favorable circumstances can all the chromioles in the same chromosome be counted. The best we can do is to approximate and average their num- ber. I have stated that in the early anaphase we find at each pole twelve chromosomes, each one containing about six more 22 EISEN. [Vou. XVII. or less distinct chromomeres, and that every such chromomere possesses about six chromioles. This makes 432 chromioles in all for the daughter-nucleus. When the nucleus of the following cell, the spermatocyte, enters the metaphase we find the chromosomes in the shape of split ”’s. The chromomeres in these are double and appear to contain each six chromioles, or seventy-two for each chromo- some. As there are twelve chromosomes, each equatorial plate should contain 864 chromioles, which, after the equation-divi- sion of the chromosomes, would again give to each daughter- nucleus the same number as formerly, or 432 chromioles. From this we are justified in assuming that during the conflu. ent umbrella stage of the nucleus the chromioles have been doubled. The easiest way to explain this increase is to assume that each chromiole has been divided in two, thus presumably preserving the quality while increasing the quantity. It is not improbable that one of the objects of the confluent umbrella stage is to allow the undisturbed division of the chromioles. The Chromoplasm. — By the chromoplasm I understand the apparently homogeneous substance which directly surrounds the chromioles during all stages of their existence, except, perhaps, while they pass through the resting stage in the polymorphous spermatogonia (Figs. 1-3). In this stage the chromioles appear to lie free in a linin thread, at least there is no visual evidence of their being surrounded by any chromo- plasm. That each chromiole is actually surrounded by a thin film of chromoplasm is, however, probable. As soon, however, as the chromomeres are beginning to form, then we can see that the individual chromioles are imbedded in a homogeneous substance for which I propose the name “‘chromoplasm.”’ It is the chromoplasm which gives the chromosomes their general form, appearance, and color. The chromoplasm constitutes by far the greatest part of the chromosomes, and it appears to be the vehicle for conveying and nourishing the chromioles. As regards the want of chromoplasm in the polymorphous nuclei, we may assume either that the chromoplasm has been disintegrated or been used up as food for the chromioles, or we may suppose that the chromoplasm has become concentrated in No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 23 the body, which I will directly describe as the chromoplast. It is quite possible that both these processes have taken place, as the chromoplasm found in the chromoplast is not sufficient to account for the quantity found in the chromosomes at a later stage. That the chromoplast has something to do with the formation of the chromoplasm is more than probable, because at the time when the spireme segments are being formed, the chromoplasm is seen to be thicker nearer the chromoplast, while at the distal end from the chromoplast the chromoplasm is thin or very thin. It sometimes seems as if the chromo- plasm had flowed from the chromoplast and been gradually distributed all along the spireme segment. It seems also prob- able that the chromoplasm is a prominent constituent in the chromoplast — at least the only visible differentiation between the chromoplasm in the spireme and the chromoplasm in the chromoplast is that the former stains less intensely than the latter. In most papers on cytology the chromosomes are figured with their margins drawn out into the linin network. I think this is probably an error caused by imperfect staining, as in all my best preparations I could distinctly see that the chromoplasm always possessed a rounded margin, and that the points consisted exclusively of linin which at times may be so stained that it cannot be distinguished from the chromoplasm. The Chromomeres. — But little need be said about the chro- momeres, as they will be again referred to in describing the evo- lution of the nucleus. The chromomeres begin to form as soon as the nucleus of the polymorphous cells enters the imperfect resting stage. The chromomeres are formed in the follow- ing manner: Two, and later three, chromioles which, during the perfect resting stage, were suspended singly in the linin, come together and are at the same time seen to be surrounded by a thin layer of chromoplasm, thus forming a small isolated body suspended in a linin network. The chromoplasm soon increases in quantity, and the chromomere is in this way in- creased in size. The number of chromioles present in each chromomere is not always the same in the early prophases, and some chromomeres may possess twice the number of chromi- oles as some others. Still the number is fairly constant, gen- 24 EISEN. [Vor. XVII. erally being three. There are more chromomeres in the early spireme stages than in the later ones, and as these early ones also are smaller, it appears as if the later chromomeres are the results of the fusion of several smaller ones. In the perfected bouquet stage there are, as a rule, about a dozen chromomeres in each spireme segment (Figs. 15, 121). Those nearest the chromoplasts are larger and possess more chromioles than those more distant. When the chromomeres split there is almost, without exception, six chromioles in each. With the splitting of the spireme segment the chromomeres again lose their identity to a considerable extent, appear smaller, and are more numerous; the chromioles also are smaller. But these chromomeres fuse again into larger chromomeres, and when in the contraction stage the bretzel-shaped chromosome is formed we find that it possesses twelve chromomeres, each one with six chromioles (Fig. 121 £). The new or daughter- chromosome, which results from the equation division of the bretzel, contains only six chromomeres, each with six chromioles (Fig. 121 7). From this time on the chromomeres gradually lose their identity, and more and more fuse together until at last, at the end of the anaphase, they have become so confluent that no trace of their original form remains. But as soon as the nucleus begins to reconstitute itself the chromomeres at once reappear (Figs. 62, 118). The number of chromioles at this time is uncertain. The following stage of growth of the nucleus is characterized by a greater separation of the chromo- meres (Fig. 119). The typical number of chromomeres in the chromosomes of the spermatocyte is the same as in the chro- mosomes of the auxocyte, or six in each. The exact number of chromomeres which go to make up a chromosome sometimes varies. Thus we now and then find chromosomes with only four chromomeres instead of six, but we may then always expect to find that some other chromosome possesses eight chromomeres, and that in this way the proper number is made up. From the above it will be seen that the chromomeres cannot be considered as permanent organs of the nucleus or more in particular of the chromosome, but that they are merely convenient forms of struc- ture, the object and function of which is to facilitate the hand- INO: Es] SPERMATOGENESIS OF BATRACHOSEPS. 25 ling of and the disposition of the chromioles. The definition of a chromomere would thus be this: A small body of chromi- oles surrounded by or imbedded in a matrix of chromoplasm, the object of which is to facilitate the growth, nourishment, and multiplication of the chromioles. Leaders. — As leaders I designate the threads or filaments of chromoplasm in which are suspended the chromioles in the earliest stages of nuclear activity. The chromoplasts which first lie free seem to attract a certain number of such threads, which radiate out in different directions from the chromo- plasts. In the beginning the leaders are of a varying number, — how many is difficult to say, but decidedly more than twelve ; but as the process goes on they diminish in number, and at the end of the process they are found to be only twelve, or just as many as the future chromosomes. The exact process of this formation has not been properly followed, but it seems as if the chromioles actually passed through the chromoplast and were projected through it into the leaders. At least we find at that time in the chromoplasts granules which greatly resemble the chromioles in size and form, besides being of the same nature as regards their staining qualities. I have often found that the free, distal ends of the leaders were twelve in number, while the ends attached to the chromoplasts were more than twelve; and this fact I can only explain by assuming that the chromioles are pushed into the leaders from the chromoplasts, or, in other words, that the free ends of the leaders are finished first and that their ends, which are attached to the chromoplasts, are the last parts to be per- fected. At the end of this process we find that there are twelve leaders which rest their free ends on the nuclear wall nearest the spheres, while their main parts are twisted and bent in the cavity of the nucleus. If this supposition is cor- rect, then the process would be something like this. The chromoplasts attract chromioles from all sides and take them up inits plasma. They are then again expelled into twelve leaders, which latter are being fed with chromioles from the chromoplasts. The leaders attached to the chromoplasts would thus be of two kinds: one set, the genuine leaders, 26 EISEN. [VoL. XVII. which pass from the chromoplasts, and the other set merely strings of chromioles which pass into the chromoplasts, again to be expelled from them into the regular leaders. The formation of the chromomeres would, of course, take place in the regular leaders, or possibly even in the chromoplasts. Auxocyte in the ‘‘imperfect resting stage,’’ showing the formation of leaders consisting of round chromioles surrounded by a film of chromoplasm. The leaders start from two chromoplasts of unequal size, both containing endochromatic granules. The leaders are connected by a linosomic network. Four linoplasts. In the cytoplasm are seen the two spheres, the inner one, the granosphere, containing the archosome. There are eight acces- sory archosomes, some in the plasmosphere, others in the cytoplasm. The two spheres are of a foam-like structure. The cytoplasm is only partially indicated. The Chromosomes. — The chromosomes are not in any sense permanent organs of the nucleus. They arise, disappear, and are re-formed as the case requires ; in fact, are mere convenient structures for the proper division and nourishment of the No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 27, chromioles. A chromosome is built up of a certain constant number of chromomeres without any other additional part than a chromoplast. A chromosome may thus be termed a string of chromomeres attached to a chromoplast. The formation of chromosomes is of a necessity different in the different varie- ties of cells. In the polymorphous spermatogonia, where a resting stage occurs in the nucleus, the chromosomes originate from leaders or strings of chromioles, in the way that has been partly described in the preceding paragraph. This is the case also in the auxocytes. The leaders finally contract, their chromomeres approach each other and finally fuse. When the required number of chromomeres have formed, the leader splits lengthwise, and shortly afterwards the two halves sepa- rate and spread out. At the same time the chromoplasts divide in as many parts as there are leaders, one part remain- ing attached to each leader (Fig. 122). The next step is a further contraction of the leader, which again is followed by a twisting of its free ends, thus forming the bretzel-shaped chromosome. The mitosis of the chromosomes will be treated under the heading of mitosis. In the spermatocytes the chromosomes appear from the confluent umbrella stage in the form of staples, with strongly marked chromomeres, and with the chromoplast attached to the angle of the chromosome instead of to the end of one of its arms, as in the auxocytes. The chromosome in each cell variety is characterized by a certain number of chromomeres ; in the auxocytes and spermatocytes they are six, though now and then we find some chromosomes larger than others. When such is the case we at the same time find very small chromo- somes with a smaller number of chromomeres, thus making the number of chromomeres and chromioles the same for every nucleus of the same kind of cell. In the mitosis of the poly- morphous cells we find the number of chromosomes to be twenty-four, but in the auxocytes, as well as in the spermato- cytes, the number of chromosomes is reduced to twelve. The reduction in number takes place in resting stages of the auxo- cyte, and is due to the chromoplasts which project only twelve leaders instead of twenty-four, as in the polymorphous cells. 28 EISEN. [VoL. XVII. In the polymorphous cells the chromosomes divide through common or somatic mitosis; in the following stages the auxo- cyte divides through heterotypic mitosis, while in the sper- matocytes the mitosis is the homoeotypic one. In the end of the anaphase of the two maturation cells the chromosomes enter an almost perfectly confluent stage, in which the individual chromosomes have lost their individuality, being fused into a single umbrella-like mass. From this mass the individual chromosomes reappear, but it seems almost incredible that the new chromosomes should be composed, each one of them respectively, of the same identical chromo- meres and chromioles as before mitosis. The changes which the chromosomes undergo in the matura- tion cells will be more particularly described under the chapter on mitosis. The chromosomes of the spermatocytes possess the peculiarity to take the congo stain after the haematoxylin, which causes them to appear reddish-black instead of pure black, as do the chromosomes of the auxocytes. The chromosomes of the auxocytes are bretzel-shaped, while those of the spermatocytes are /-shaped before mitosis. The bretzel form is due to the fact that the ends of the chromo- somes overlap each other instead of growing together. The chromosomes in all these varieties of cells divide by equation division, and not by reduction division. The Chromoplast and the Endochromatic Granules. — This body, which I consider to be of the greatest importance in the evolution of the nucleus, has been variously known as nucle- olus, netknot, karyosome, etc., but as these names have also been applied to other structures in the nucleus, I consider my- self justified in proposing for it a new and more distinct name, the ‘‘chromoplast,” thus indicating at least one of its char- acteristic properties in connection with the chromosomes. In the Batrachoseps testes the chromoplasts are most dis- tinctly individualized in the resting stages of the nucleus, and in those stages in which the chromosomes have not yet reached their final and perfect form. They may, however, still be seen in the metaphase of the auxocytes, but after that stage is passed, they become less distinct, or may even so fuse with the chromo- No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 29 somes that they cannot always be distinguished from them. In the resting stages, however, the chromoplast or chromoplasts, as there may be several, stand out quite distinctly and individual- ized and can then be studied to the best advantage. This refers not only to the resting stages of the polymorphous nuclei, but also to those of the auxocytes, the spermatocytes, ° So 6° ° ary i) ° ° ¢ ° ° ° ° A polymorphous spermatogonium in the “‘ perfect resting stage.” The form of the nucleus allows the most perfect metabolism. Numerous chromioles are connected by a thread of chromo- plasm. A network of linosomes is partially indicated, the individual granules being con- nected by linopodia. A large, oblong chromoplast with endochromatic granules. Eight parachromatic granules. A single archosome in the cytoplasm, the latter only partially indicated by small open circles. A single large, round linoplast, with seven endonucleolar granules. and the spermatids. In the two first-named cells, which also are the largest, they offer the best facilities for study. In the perfect resting stage of the polymorphous nucleus we find always one, but sometimes two or more chromoplasts, easily distinguished by their capacity for intense staining. When the iron-haematoxylin-congo stain is used the chromo- plasts become stained, as a rule, most intensely black, while the true nucleoli, or linoplasts, take the congo and become red. The chromoplasts are also characterized by possessing 30 EISEN. [VoL. XVII. in their interior several highly refractive bodies which I have termed ‘‘endochromatic granules.” These granules never occur in the true nucleoli, which fact always enables us to distinguish between them and the chromoplasts, even in instances when the true nucleoli are stained darkly, as sometimes happens. The endochromatic granules never stain, but appear to be naturally of a yellowish color and always highly refractive. They vary in size, and are sometimes so small that their refrac- tivity is not readily perceived, they appearing only as minute granules of an intensely dark color. But as they increase in size we begin to see in their center a light-colored, highly bril- liant spot, which, in the larger granules, is correspondingly large and distinct. These refractive granules are almost invari- ably present, and they may be truly termed “landmarks,” by which we can determine the position of the chromoplast. Even in places where the chromoplast itself cannot be dis- tinguished we can judge of its presence by one or more of these endochromatic granules, as, for instance, in the metaphase and anaphase of the auxocytes. It is the presence of these gran- ules which enables us to follow with certainty the evolution of the chromoplasts, and to ascertain their presence in every stage of the nucleus. The number of granules in each chrorhoplast is in no way constant and seems to be of no great consequence. Some are perfectly round, others are angular, and their general appearance seems to indicate that they constitute secreted matter, or metabolic products, probably for the attraction and nourishment of the chromioles. While each granule is highly refractive in the center, its outline is, on the contrary, very dark, so dark indeed that it would almost seem as if it was surrounded by a shell of some particular substance. Whether that is the case, or whether the dark margin is only the effect of refraction, I have not been able to ascertain. In the small chromoplasts attached to the chromosomes in the metaphase we sometimes find one or two endochromatic granules, sometimes also none. In the confluent umbrella stage of the nucleus we generally find a larger number of granules which appear to have been newly secreted. They disappear at the end of the umbrella stage, though a few may remain even after the nucleus has No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 31 begun to reform and after it has fairly entered its stage of growth. For characteristic figures illustrating the endochro- matic eranules see: Pigs: 2, 9, 21, 26, 57-62, 121. The chromoplasts are generally rounded in outline and well defined. When insufficiently differentiated and overstained they frequently appear to be star-shaped and very irregular, but this is merely an effect of the overstaining. While the form is always rounded, it is not always globular, but, on the contrary, oblong or beaded, especially in places where we expect a division of the chromoplast. In the earliest stages of the polymorphous nuclei the chromoplast is generally oblong or consists of two distinct beads (Figs. 1-3). It lies then iso- lated in a vacuole, only surrounded by linin threads radiating from it in every direction. Ata later stage the chromoplast is seen to be in more or less intimate connection with the leaders on which the chromioles are suspended. To begin with this connection is very slight (Fig. 3), but later on it becomes more intimate, and leaders with chromioles are seen to start out in all directions, radiating from the chromoplast like the radii from the center of a circle. When there is more than one chromoplast, leaders connect with all. Some chromoplasts, however, may be connected with more leaders than others (Figs. 8, 9). In the last resting stages, when all the leaders have formed, it will be seen that all of them connect with the chromoplasts in such a way that if, for instance, one of the chromoplasts is connected with only four leaders, the other is found to be connected with the bal- ance, z.¢., eight ; there are always as many leaders as there will be chromosomes. The chromoplasts appear thus to attract the leaders, and my opinion is that in this manner the chromosomes are formed. We can follow the chromoplasts with certainty up to the end of the anaphase. In the bouquet stage, where the spireme segments begin to separate from each other, it will be seen that this separation is caused by a division of the chro- moplasts into several parts. In the perfect bouquet stage we thus find that two or more spireme segments are held together by a single chromoplast (Figs. 14-16). The ultimate result of this division is undoubtedly to so divide the chromoplast 32 EASE. [VoL. XVII. that one part will remain attached to each chromosome. This is also undoubtedly what takes place, as in the metaphase when the chromosomes are all perfectly formed and placed on the central spindle in the form of rings, we find that at the center of one side of each ring is a globular body, frequently An auxocyte in the ‘‘bouquet stage.”? There are twelve leaders starting from five chromo- plasts. The leaders consist of chromomeres containing chromioles suspended in a film of chromoplasm. The spheres are of a foam-like structure. There are three acces- sory archosomes and one archosome with two centrioles. The open space between the inner granosphere and the outer plasmosphere represents the hyalosphere. The cytoplasm is only partially indicated. containing one or more endochromatic granules. These bodies attached to the chromosomes are, therefore, chromoplasts. In the confluent umbrella stage the endochromatic granules are the only indications of the presence of the chromoplasts. This is the case in the auxocytes. In the spermatocytes the chro- moplasts are much more difficult to follow, but the greater Now rs] SPERMATOGENESIS OF BATRACHOSEPS. 33 : thickening of the chromosomes at the place where they are bent makes it probable that the chromoplast is situated at this point (Figs. 118, 119). In the mitosis of the spermatocyte I have not been able to affirm with certainty the presence of chromoplasts, except in the umbrella stage, where their presence is indicated by endochromatic granules. Again, in the resting stages of the spermatid the chromoplasts, generally one or two, are plainly definable, especially by the means of the congo-thionin-ruthenium red-staining method. In the resting stages of the auxocytes, which are especially favorable for study, a stream of chromoplasm is seen to project from the chromoplast to each leader, and each leader is more densely stained in the parts nearest the chromoplast. I do not, how- ever, consider it with certainty established that a flow of chro- moplasm actually takes place, as the phenomenon of deeper staining can also be explained by a greater attraction of chro- moplasm in proportion as the chromoplast is approached. If this latter supposition is the true explanation, then we must also look for the source of the supply of chromoplasm else- where, possibly in the parachromatic granules. Be this as it may, the observed facts warrant us in con- cluding that the chromoplast is of the utmost importance in the formation of the chromosomes, and that its function seems to be to attract the leaders, to segregate and define the chromo- somes, and perhaps, in a general way, to supervise the formation and evolution of the chromosomic constituents of the nucleus. Chromoplasts are probably present in all nuclei, and probably also in all chromosomes. They have been frequently con- founded with true nucleoli, but their distinct nature has also been recognized by many investigators, and in all recent bio- logical papers they are both described and figured as being of different nature from that of the so-called true nucleoli. In many instances, however, they have undoubtedly been over- looked, especially in nuclei in the bouquet stage, where they often are so small that they can only be distinguished through their endochromatic granules, the presence of which always indi- cates that the object in question is actually a chromoplast, and not a true nucleolus or linoplast. 34 EISEN. [VoL. XVII. ‘ Parachromatic Granules. — As parachromatic granules I designate a class of dark-staining granules which, during the resting stages of the polymorphous nucleus, are found in the vicinity of the chromoplast (Figs. 1-8). These granules stain in the same manner as the chromoplasts, and I have not been able to differentiate them by color. When the leaders are formed these granules are the first ones to join the leaders, and it suggests itself that possibly they furnish the necessary chro- moplasm for the leaders. But as the aggregate of all these parachromatic granules does not equal the mass of the chromo- somes we must suppose that, if the parachromatic granules furnish the chromoplasm, they cause it to be evolved and that they do not furnish it alone from the amount stored in them. The parachromatic granules are of various sizes and forms and vary also as regards number. With certainty they are only found in the polymorphous cells. Linoplasts, or True Nucleoli.— The linoplasts are that kind of nucleoli which supply and nourish the linin during certain stages of the mitosis. When properly differentiated with congo they appear rather transparent and of a reddish-orange color. They are thus readily distinguished from the chromoplasts which take the iron-haematoxylin stain with great avidity. The number of linoplasts is variable; sometimes we find only one, sometimes again there are five or six. In the auxocytes the linoplasts are most numerous just before the stage in which the spireme segments are split, after which they gener- ally disappear. Rarely one is left at the metaphase, and when this is the case it is thrown out into the cytoplasm and evi- dently dissolved. During the separated spireme stage the lino- plasts are seen to dissolve, apparently giving off particles to the linin network (Figs. 12-17, especially 14). This is also the very period when the largest quantity of linin is required for the pulling apart of the two halves of the spireme segments. If we to this observation add the one that the linoplast consists of apparently the same kind of granula as the linin network, both as regards size, form, staining reaction, etc., we are, I think, justified in assuming that the linoplast actually does furnish the extra linin required for the pulling apart of the spireme leaders. No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 35 As regards the nature of the shell of darker granules surround- ing the linoplasts, I have not any observations. This shell seems to exist only during the resting stages of the polymor- phous nuclei and not in the maturation cells. Besides pure linin granules the linoplast undoubtedly also contains secretions with which the linin is nourished. The function of the lino- plast appears thus to be not only to furnish stored-up linin, but also to nourish the general linin network. I hardly need to point out that the linoplast has been variously termed paranu- clein, pyrenin, true nucleoli, Kernkorperchen, etc. Linin.— The linin network is not difficult to differentiate, as with the congo-iron-haematoxylin method it stains reddish- yellow, while nearly all other structures take a black or at least a gray stain. When insufficiently differentiated it some- times appears as if the chromatin of the chromosomes extends far out into the linin network; and in this way it is generally figured. With proper differentiation, however, it is seen that this is not the case, but that the chromatin is never extended into the linin, at least never as a fine thread (Figs. 14, 24, I19, etc.). As long as the nuclear membrane is unimpaired the linin always has the appearance of fine network, com- posed of granules of equal size and form. These granules occur either singly or in small groups, which latter may be mistaken for larger granular units. In Figs. 14 ¢ and 26 41 have figured these granula in the way they appear under the most favorable optical conditions, though the individual gran- ules are perhaps somewhat more rounded than they appear in the illustrations. We must distinguish between two distinct periods in the life cycle of the linin, one being the periods of rest, the other the periods of activity. There are two periods of rest. One is found in the resting stage of the nucleus before the leaders have properly formed, and the other occurs later in those stages of mitosis in which the nuclear membrane has been dissolved, and the linin been scattered away from the chromosomes. In the former of these stages the linin gran- ula are more regular than in the latter (Figs. 1-3, etc., also Figs. 26, 37). After the nuclear membrane has been dissolved the linin network is carried away from the chromosomes, and 36 EISEN. (Vo. XVII. the granules are found both evenly distributed and arranged in larger heaps. The active stages of the linin are to be found during the prophases, during the formation of and the separa- tion of the leaders. It is during this period that the lino- plasts are dissolved in order to supply the necessary and extraordinary linin required for this process. The linin is then seen to consist of a network attached to the chromosomes or spireme segments, while part of it spreads out through the nucleus as irregular bridges between the chromatin segments. The linin possesses thus two distinct qualities, one being that of supporting the chromioles, chromosomes, or chromatin parts generally, the other being that of separating the two split spireme or leader halves from each other. As soon as this lat- ter process is accomplished the linin is dispersed, at first all through the nucleus, and later on through the cytoplasmic part of the cell. The mass of the linin is composed principally of one kind of granules—the kind here always referred to as the linin granules. This general granule stains reddish or gray according to the process of differentiation. But in these granula we also find scattered isolated granules which stain only with the iron-haematoxylin stain (Fig. 26 6). Of the nature of these granula I have no knowledge, but it suggests itself to me that perhaps these denser appearing granula may serve as a support for the other kind, insuring an equal or at least a proper distribution. It will be seen that during the period of activity the linin granule stains differently from what it does when in rest. This differentiation is, however, only brought out by the achromatic light-filter mentioned elsewhere. With the use of this filter we find that the linin granule during its activity stains bright and light red, while during the periods of rest it stains dark gray. This differentiation also allows us to follow the linin granules through the cytoplasm after the nuclear membrane has been dispersed. What finally becomes of these linin granules is uncertain. But I have no observations which would indicate that they reconcentrate themselves in the new daughter-nuclei. On the contrary, there is no sign of any accumulation of linin granules in the immediate vicinity of the Noe Fa] SPERMATOGENESIS OF BATRACHOSEPS. 37 new nucleus, and the first appearance of the linin in the new nucleus is found close to the new chromosomes. This new linin is, to begin with, of limited quantity, and it appears as if it were actually re-formed, probably from some linin granules with a generative function. In such case the majority of the linin granules are either absorbed by the cytoplasm or used up in the formation of the new nuclear membrane. The Nuclear Membrane.—The nuclear membrane has already been referred to in connection with the cytoplasmic membrane and cell wall. The most favorable cell for the study of the nuclear membrane is the large auxocyte in the beginning of the chrysanthemum stage. In this stage the new nuclear membrane is being reconstituted. In case the nuclear mem- brane is formed by a thickening of or by an accumulation of cytoplasm, we should expect to find such cytoplasm in the immediate vicinity of the place where the new nucleus is to be formed. No such accumulation of cytoplasm exists at this place. On the contrary, a false, or rather an accessory cyto- plasmic membrane has previously been formed around the nucleus, but at some distance from it (Figs. 62, 70). The object of this membrane is to enable a vacuole to form, in which the new nucleus can have ample space for development. While this membrane is yet in existence the nuclear membrane is formed around the new nucleus. As at this time there is no cytoplasm between the cytoplasmic membrane and the chromosomes, the new membrane must be formed of other matter than cytoplasm. It is probable that this other sub- stance is linin, of which there is at this time a fair supply around the chromosomes. As to the dissolution of the nuclear membrane it is most interesting to note that, at least in the auxocytes, the mem- brane is dissolved only after the chromosomes have formed. The spindle fibers and mantle fibers cannot, therefore, have anything to do with the formation of the chromosomes. The nuclear membrane always disintegrates first at those places where it is first touched by the fibers of the mantle. The cen- tral spindle has apparently nothing to do with the dissolution 38 EISEN. [VoL. XVII. of the nuclear membrane, which is fully dissolved before the fiber of the central spindle has reached its immediate vicinity. Phylogeny of the Nucleus.—It seems probable that the perfect resting stage of the nucleus, such as is seen in the polymorphous spermatogonia of the testes of Batrachoseps, represents a phylogenetically primitive nucleus, in which the necessity for the formation of chromosomes and chromomeres has not yet made itself felt. In the most primitive nucleus we should expect to find only a limited number of chromioles, which might be readily manipulated by the chromoplast without the assistance of chromomeres and chromosomes. But as the development of the species progressed and more characteristics were accumulated, we may presume that more chromioles were required, perhaps in order to propagate these characteristics. With this increase in the number of chromioles a more compli- cated system of mitosis became necessary ; hence the very com- plicated apparatus of spindles, etc., accompanying the mitosis of all higher cells. In the lowest forms of animal and plant life the chromioles were probably scattered in the cell itself, just as we now find them in the nucleus of Trachelocerca, a flagellate infusorian described by A. Griiber. In this instance there can be little doubt as to the nature of the granules and that they are real chromioles. The granules found in many bacteria resemble also greatly the chromioles of the higher cells; and it may be possible that in these low organisms the chromioles are only suspended in the cytoplasm, without any surrounding nuclear wall. In the blue-green algae, the Cyanophyceae, we have probably a similarly primitive nucleus, in which the chromomeres and the chromosomes have not yet been developed. In a later stage we should expect nuclei with a nuclear wall, but with the chromioles free as in the perfect resting cells in the testes of Batrachoseps. As is well known, many investigators deny the existence of nuclei in the Cyanophyceae and contend that the darker staining substance in the center of the cell is nothing but condensed cytoplasm. But this theory seems to me unten- able in view of the fact that the Cyanophyceae are highly dif- ferentiated plants which certainly would require hereditary No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 39 granules for the transmission of characters. If, as I suppose, the chromioles constitute these granules, then it is probable that we have to identify the denser protoplasmic mass in the cell of the Cyanophyceae as being chromioles and not cyto- microsomes. In connection with this question it is interesting to note that the nucleus of leucocytes, both in batrachians and in man, contains only a few chromioles. The Archosome. The Archosome Proper: its Structure, Centrosphere, Somo- sphere, and Centrioles.— As the archosome I designate that particular structure which takes part in the radiosomic process of the cell, and which is situated at .the very pole of the spin- dle, at least during certain stages of the mitosis. The archo- some consists of the following parts: One or more interior granules — the centrioles of Boveri. Surrounding them we find a generally very thin zone or sphere — the somosphere. Both the centrioles and the somosphere stain deeply, the centrioles much more so than the somosphere, and it is sometimes difficult to distinguish An archosome consisting of an onewromythe other, 1) believe, the word « \ citer:cenaauhere fan tinier somosphere, with two cen- trioles. “centrosome” might, with advantage, be retained to designate this inner part of the archosome, consisting of centrioles and somosphere. Next outside of the somosphere we find a larger, generally non-stainable, achromatic zone — the centrosphere. This zone is, however, not always achromatic, but takes the stain under certain conditions and stains then with plasma stains. Usually this centrosphere is figured as a round disc, with a perfectly circular outline, giving one the impression of being nothing but a vacuole, in the center of which is situated the centrosome proper. This description of the centrosphere is, however, not quite correct. While the centrosphere is fre- quently circular in outline, it is not always so; indeed, I think that in the majority of instances it is not circular, but of an amoeboid form. 40 EISEN. [VoL. XVII. We see projections starting out just like the pseudopodia of an amoeba, and I have no doubt that these projections must actually be considered as true amoeboid projections, serving the very same purpose as do the pseudopodia of the amoeba, that is, as organs of locomotion and perhaps also of prehension. Unless we assume the existence of a special organ for the movement and propulsion of the archosomes and the accessory centrosomes, their movements and migrations from one part of the cell to the other are simply unaccountable. But if we assume, as our observations warrant us in doing, that the centrosphere is an organ for the propulsion of the archosome, then these movements become easily explainable. This theory is yet more affirmed by the fact that the centrosphere is amoe- boid in almost every instance in which from its position we can consider it to be in activity, and in the act of moving from one place to another. On the contrary, when we have reaons to expect the archosome to be at rest, we also find that the centrosphere is globular or disc-shaped instead of amoeboid. This holds good also in regard to the accessory archosomes, though with them it is more difficult to determine when they are at rest and when in activity. We are therefore, I think, justified in assuming that the archosome, as well as the accessory archosomes, propel them- selves from one place to another by means of the amoeboid centrosphere, which sphere, when at rest, assumes a globular form, but when in activity shows an amoeboid margin, or pseudopodia. The position of the archosome is variable, according to the stage of development of the cell. It may be said, as a rule, that the archosome is situated either in the granosphere or in the plasmosphere, when both these spheres are present. In the prophases of the auxocyte, in which the two spheres attain their highest development, the archosome is generally found in the granosphere. It then generally possesses two centrioles which are either surrounded by acommon somosphere or are sufficiently apart to have a separate somosphere for each centriole. The archosome seems to move around in the two cytoplasmic spheres in a most independent manner, sometimes being found No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 41 in the granosphere, sometimes again on the circumference of the sphere. At other times it is found a considerable distance out in the plasmosphere. It is at times impossible to distin- guish the true archosome from the accessory centrosomes, as their structure is similar, though we might, with considerable certainty, assume that the body with two centrioles situated in or on the granosphere is the true archosome, but even about this we cannot always be certain. Sometimes there is more than one such body in the granosphere, while, on the other hand, two-centrioled bodies are also found in the plasmosphere. Even when the central spindle is being formed, and at a time when the archosome is situated at the pole of the aster, we find in the cytoplasm bodies in no apparent way differing from the archosome. At other times we find what appears to be the true archosome connected by a thread-like process with one or more accessory archosomes (Figs. 10-17, 27-33). This thread-like connection is the remains of the somosphere which has been pulled out from the original somosphere surrounding the archosome from which the budding took place (Fig. 14 a). Such rings of somosphere are seen almost in every cell, often in considerable numbers. Why the thread assumes the form of a ring is not quite apparent, but may be explained by sup- posing that it follows the inner walls of a vacuole. This will, however, not explain all forms, as in many instances the thread on which the centrosomes are suspended circles around the granosphere, or seems otherwise to be entirely buried in the cytoplasm. In other instances the granules connected by the thread are also suspended on the rays of some fiber cone or on some spindle cone. The granules so suspended are not as a rule all of the same size and staining capacity, as some will stain intensely, while others adjoining hardly stain at all. Frequently this loss of staining capacity decreases as the gran- ules are situated farther away from the archosome or accessory archosome from which they budded. The same also often holds good as regards size, those farthest away being the smallest. To this general rule there are many exceptions; small and large granules often alternate, and so do darkly stained ones, with those that are lighter. 42 EISEN. [Vor. XVII. As a result of my observations I have come to the following conclusions in regard to the nature, position, and functions of the archosome. The archosome is a specialized accessory archosome, special- ized for the purpose of conducting the radiosomic process of the cell. During the resting stages of the cell the archosome is generally, but not always, situated on the axis of the cell; during mitosis the archosome is situated at the pole of the cen- tral spindle. The archosome gives rise to the accessory archo- somes by budding, and, vzce versa, an accessory archosome may take the function of an archosome. As the archosome is, as a rule, found in the concave part of the granosphere, its peculiar and distinct qualities may depend on some particular food or stimulus furnished by that sphere. As regards the functions of the archosome in connection with the spindle fibers, we find that the mantle fibers, as well as the central-spindle fibers, start out from the outer margin of the centrosphere and do not connect with the somosphere or with the centrioles. I have found this to be the case in every instance where I could see the pole of the spindle in a favor- able manner. The fibers or rays are thus not inserted in the somosphere, but simply join the outer surface of the centro- sphere. The only rays which are in actual contact with the somosphere are the contractile fibers, or those fibers which attach themselves to the chromosomes for the purpose of pull- ing them apart. The main part of the contractile fibers starts also from the exterior margin of the centrosphere, but each fiber is seen to be connected with the somosphere by a very thin thread of dark-staining substance (Figs. 110-113). In the early resting stage of the polymorphous cells some- times neither archosome nor accessory archosomes can be dis- tinguished. Whether they are at such times situated in the nucleus or are not stainable I am unable to decide upon, but the former seems to me the most probable. In many such resting cells we find one or more darkly staining bodies which, however, are seldom situated in the axis of the cell. As soon, however, as the granosphere has assumed a definite form the two-centrioled archosome is seen to be situated in its center, No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 43 or rather in its concavity. At the poles of the central spindle we find always one and generally two archosomes. Sometimes the two are connected by a thin thread of somosphere. Some- times this thread is double, the two archosomes being situated at the opposite ends of a dark-staining ring. At the end of the anaphase the archosomes have gradually diminished in size and staining capacity, and are then only visible by the most careful optical manipulation. I have no doubt that in in- stances where the archosome has not been figured in this stage of mitosis, the failure to observe it is referable to insuffi- cient optical means, and not to an actual absence of the archo- some. In the confluent umbrella stage the archosome is, however, not to be distinguished. But at this stage the apex of the central spindle has also disappeared, to reappear later on below the nucleus. With its reappearance an archosome with a single centriole is also seen at the pole of the fibers, and we may with some reason presume that it is the same one that was previously situated above the nucleus, but which has followed the central spindle and been pulled through the ring-like nucleus (Figs. 54-61, 63, 64, 69, 70). As the granosphere is reconstituted around or near this pole, it follows that the archo- some will be found in or near the new granosphere. But if the same archosome will always perform the same function in the new cell is doubtful; it frequently appears as if the place of the archosome in the new spermatocyte was taken by some accessory archosome, already at the pole of some spindle cone. The Accessory Archosomes, their Structure and Functions. Expulsion of Superfluous Archosomes. — As the accessory arch- osomes have already been referred to in the preceding para- graph, I will here only describe a few points not yet touched upon. We have seen that the accessory archosomes are quite numerous, but of varying number. In the earliest stages of mitosis they are more numerous than in the later ones, and it appears that they are in some manner used up. At first they circle around in the spheres apparently without any regularity ; later on they arrange themselves around the archosome at the pole of the central spindle. My observations are not conclu- sive, but they tend to show that the accessory archosomes 44 EISEN. [Vox. XVII. either direct or actually furnish some substance to the contrac- tile fibers. They are, during the metaphase and anaphase stages, found in close proximity to the points from which these fibers start, and in several instances I have seen them actually in contact with those fibers. It seems possible that an acces- sory archosome is first placed in position on the outer side of the centrosphere, and that it then gives rise to a contractile fiber by budding (Fig. 111). Again at other times (Fig. 110) we find these contractile fibers already formed, and yet in their vicinity a number of accessory archosomes, arranged in a ring around the archosome. Be this function of the accessory archosomes as it may, certain it is that they also possess another function of great importance, that of presiding over the fiber cones and the pulling of the cytoplasmic membrane away from the nucleus, while the latter is in a stage of growth (Figs. 65-71, 114-116). Thus at the end of the confluent umbrella stage we find them at first situated on the cytoplasmic membrane with fibers radiating out in several directions. They soon, however, rise from the membrane, carrying with them the fiber cones. As the ends of the cones remain attached to the membrane, the latter is naturally pulled away from the nucleus. There may be one or more accessory archosomes at the pole of each fiber cone. When the fiber cones have per- formed their function the accessory archosomes slide down along the fibers and congregate in the vicinity where the new granosphere is being reconstituted. This refers to the sper- matocytes, as I have not found any fiber cones in the auxocytes. Towards the confluent umbrella stage in the auxocytes the accessory archosomes diminish in size, number, and staining capacity, just as does the archosome. They next reappear on the cytoplasmic membrane, but are not readily detected except on sections which pass obliquely or excentrically (Fig. 65). A most interesting fact is that a large number of accessory archosomes are thrown out of the cell into the intercellular spaces, in which they sometimes remain free, sometimes re- main attached to the outside of the cell membrane. (See the chapter on paracellular bodies.) The centrioles in the archo- somes vary in size and number. No.1.] SPERMATOGENESIS OF BATRA CHOSEPS. 45 IV. SPINDLES AND SPINDLE FIBERS. General Remarks. The various fibers and rays which form during mitosis may be conveniently divided into six more or less distinct classes, as follows : central-spindle fibers, mantle fibers, polar fibers, con- tractile fibers, cone fibers, and the retractile fibers of the spin- dle cones. With the exception of the contractile fibers, which possibly may be of archosomal nature, all the others are de- cidedly of cytoplasmic origin; none can be shown to be of nuclear origin. All these various kinds of fibers stain in about the same manner, readily taking the congo stain, with the exception of the contractile fibers, which retain the iron- haematoxylin longer than any of the others, and thus under proper treatment appear quite dark, even by their color indicat- ing a different origin. Their structure is also from the begin- ning different, showing distinct beads. We will now consider each of these classes more in detail. Mantle Fibers, Polar Fibers, and Central-Spindle Fibers. As these fibers have the same origin and otherwise resemble each other they may most conveniently be considered together. The central-spindle fibers are the first ones to appear during the radiosomic process. As the two centrioles, with their somospheres, move apart, there appear between them two darkly staining, narrow threads which apparently help to push the archosomes apart. Between these two threads the lighter staining central-spindle fibers begin to appear, but only after the centrosphere has separated in two parts, one to each archo- some (Figs. 37, 38). The central-spindle fibers thus originate from the outer edge of the centrosphere, just as do the polar fibers and the mantle fibers. But while the polar fibers and the mantle fibers are fed only from the cytoplasm proper, the central-spindle fibers receive, almost at once, material from the granosphere. At a very early stage we see numerous rays projecting from the archosome to the granosphere, and this radiation is so arranged and limited that, on the side 46 EISEN. [Vor. XVII. turned towards the granosphere, all rays which do not strike the granosphere must be counted as mantle fibers and polar fibers and not as belonging to the central-spindle fibers (Figs. 41-47). In order to supply this matter to the central spindle, the granosphere dissolves from the side that is turned towards the central spindle and not from the opposite side. As the o ° ° & An auxocyte in the beginning of the anaphase. Only a few of the chromosomes are indicated. At each pole there are respectively one and two archosomes and three and four accessory archosomes. The chromosomes contain chromioles suspended in chromoplasm. At the apex of each chromosome there is seen a chromoplast with endochromatic granules. To the right and left in the cell are seen agglomerations of plasmosphere indicating the position of the new cell wall, which is to separate the two daughter-cells. The chromo- somes are seen to be connected with the centriole by contractile fibers, the latter con- sisting of granules enclosed in a common sheath. ‘The spindle fibers as well as the polar fibers start from the centrosphere. central spindle grows in size, the granosphere is seen to dimin- ish. The rays of the central spindle are also seen to end in the granules of the granosphere, and the whole appearance is such as to leave no doubt of the central spindle being fed prin- cipally on the granules and secretions of the granosphere. On the contrary, no such connection can at any time be seen between the polar and mantle fibers on one side and the grano- NOT] SPERMATOGENESIS OF BATRACHOSEPS. 47 sphere on the other. These two classes of fibers are apparently only fed from the cytoplasm proper and to a limited extent also from the granules of the plasmosphere, and this latter probably only during the metaphase of the mitosis. At that time many of the mantle fibers are seen to end in the granules of the plasmosphere (Figs. 48-56). Also during the early anaphase such connection between the mantle fibers and the plasmo- sphere granules may be observed. The polar fibers and mantle fibers sometimes reach the cell wall and connect directly with it, but generally the fibers end in a marginal layer of alveoles, which, however, is never as regular as that figured by Biitschli and his school. These two classes of fibers at the end of mitosis resolve themselves into plasmosphere and cytoplasm proper, while the central-spindle fibers reconstitute themselves into granosphere, or remain for a long time comparatively unchanged as a spindle bridge between two cells. There can be no doubt as to the continuity of the central- spindle fibers from one pole to the other. In the later stages of the anaphase when the central spindle is being contracted we can follow without any difficulty the whole course of one or more fibers from one pole to the other (Figs. 57-62). hese continuous fibers are much thicker than the early fibers of the central spindle, and it appears to me as if they origi- nated by the fusion of several of the earlier fibers. At this stage of the central spindle the various fibers constituting the same vary greatly as to thickness as well as to structure. While some are very thick, others again are as thin as they were in the earliest stages of the spindle. Some of the fibers are beaded like the contractile fibers, others are smoother (Fig. 59) and show only the original structure of alternating granules. The origin of the central spindle of the spermato- cyte is less clear. Here the mantle fibers appear first, being reconstructed fiber cones. These mantle fibers meet and form a very wide spindle (Fig. 94) with very deeply sunken poles. At a later stage the central spindle is found inside of this wider mantle spindle, but as regards the process by which it is formed, I have no satisfactory observations upon which to base any theory. 48 EISEN. [Vou. XVII. Contractile Fibers. This class of fibers is of sufficient importance and interest to be treated of separately. Their origin is different from that of other fibers, and they also appear, partially at least, to con- sist of a different kind of protoplasm. They are the only fibers which connect directly with the somosphere and which thus penetrate the centrosphere. As to the actual beginning of the contractile fibers, there are no satisfactory observations, and we do not know if the narrow thread in the centrosphere orginates previous to the part outside of the centrosphere, but I am inclined to think that this thin thread is formed after the balance of the fiber. The number of contractile fibers is the same as the number of the chromosomes, as there is a special fiber for each chromosome. These fibers show from the begin- ning a different structure from any of the other classes of fibers, being from their first appearance beaded (Figs. 41-54). Each fiber is composed of a thin outer sheath which is too small to allow of its structure being perceived. Inside of this sheath the protoplasm of the fiber is distinctly beaded in a manner that greatly reminds us of the cytoplasmic arrangement of the muscle fiber. These beads are not always of the same size, those in the middle of the fiber often being the largest. There is never more than one row of beads, which begins on the outer side of the centrosphere and extends to the immediate vicinity of the chromosome. Just before the fiber reaches the chromo- some it divides into two tiny branches or arms, each arm con- necting with different points of the chromosome. As soon as the chromosome has reached the equator the contractile fiber begins to contract, becoming thicker and shorter as well as darker staining. When the confluent umbrella stage is reached the fibers lose their intense staining capacity and finally disap- pear. As regards this disappearance there are several conjec- tures possible. Either the fibers are entirely absorbed and changed into cytoplasm, or they are condensed into accessory archosomes which reappear on the cytoplasmic membrane, at this time re-forming at a short distance from and around the nucleus. Or we may even suppose that they follow the central No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 49 spindle and are pulled through the nucleus, later to reappear as retractile fibers, emanating from the apex of the spindle cone. Against the latter assumption speaks the observation that these retractile fibers are not beaded. It seems more probable that the retractile fibers are new formations, and that the contractile fibers have condensed into accessory archo- somes, now appearing on the cytoplasmic membrane around the nucleus. (See explanation of Fig. 112, p. 116.) Fiber Cones and Retractile Fibers of the Spindle Cones. As spindle cones and their retractile fibers, I designate structures which appear below the nucleus at the end of the anaphase and from which radiate numerous fibers towards the place where the new membrane, separating the two daughter- cells, is being formed. These fibers radiate from a small arch- osome at the apex of the central spindle and end partly in the granules and secretions of the plasmosphere, partly in the cell wall. The separation of the two daughter-cells seems entirely due to these retractile fibers (Figs. 59-61), which are the only ones so situated that they can accomplish such a separation. The plasmospheric granules situated in this immediate vicinity also indicate that they are used up in the construction of this membrane. The ultimate fate of these retractile fibers is a reconstitution into cytoplasm, and perhaps into plasmosphere. They disappear very soon, long before the fibers of the central spindle. We have yet to consider the peculiar and unusual structures which I have designated as fiber cones, the origin of which is as follows. A new cytoplasmic membrane is formed exterior to the nucleus, and on this membrane are found a number of accessory archosomes. From these archosomes fibers radiate on the membrane in all directions. Later the archosome rises and pulls the membrane with it, and we then get a cone-like structure (Figs. 66-74) which in time pushes out the cell wall. Later on these cones again move inward, and at a yet later stage they dissolve into cytoplasm proper. I have already suggested that these cones help to form a cavity around the nucleus which enables the latter to increase in size and develop. 50 EISEN. [VoL. XVII. As far as I know, similar fiber cones have not been observed in any other animal cells, though I have some reason to think Two daughter-cells of an auxocyte connected by a spindle bridge. There are eight accessory archosomes at the apex of as many fiber cones. Two archosomes are connected by a cen- tral spindle. In the latter is seen a mid-body consisting of three condensation granules. The chromosomes are being regenerated, and the chromoplasts appear at the angle of the chromosomes instead of at the apex, as in the last cell stage. In one nucleus are seen five, in the other six chromoplasts with endochromatic granules. Between the true nuclear membrane and the false membrane is an open space caused by the false mem- brane being pulled away by the fiber cones. that the auxocytes of Batrachoseps are not the only cells which possess them. Dr. W. J. V. Osterhout has kindly shown me a preparation of the testes of Triton cristatus, in which I could No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 51 plainly recognize a couple of fiber cones, though they were much smaller than in the testes of Batrachoseps. These Triton testes had been fixed in Flemming’s chromo-osmic-acetic mixture. The spindle cones, which Osterhout has described from the mitosis of the pollen cells of Equisetum, are exceedingly interesting, as they recall the fiber-cone structures in our present cells, even if their nature and origin be found to be entirely different. In the pollen cells the mitosis begins with spindle cones, while in the testes of Batrachoseps the mitosis ends with fiber cones. Spindle Bridge and Mid-Body. The spindle bridge is, as is now fully known, the remains of the central spindle. After this spindle has passed through the nucleus its fibers begin to diminish in number, several fibers apparently fusing into one. I judge that such is the case, be- cause as the fibers decrease in number they increase in thick- ness without getting much shorter. At this stage the fibers also show a beaded structure in the same manner as the con- tractile fibers, though not quite so pronounced. This beaded structure is also found in the fibers of the fiber cones (Fig. 116), but not in any of the mantle fibers. The spindle bridge remains a long time after the cells have otherwise separated, and in places we find not only one such bridge in the same cell but two, both starting from the same place but in different directions, and connecting several cells with each other (Fig. 32). The object of the cell bridge is probably to prevent the cells from moving too far apart, and the formation of the mid-body is perhaps only a quick way to dispose of the cytoplasm of the cell, until it can be properly absorbed in the regular way by the spheres. I have in another place suggested that the contemporaneous beginning of certain stages in the mitosis by all the cells in the same pocket may be due to some influence exerted or communicated by the spindle bridge. This body is the only visible connection between one or more cells in the same pocket. The spindle bridges are only found between cells which simultaneously begin the same stage of mitosis. 52 ELSE IN. (VoL. XVII. The mid-body is found on the central spindle at the end of the anaphase and is, as has been often described, formed in a vacuole between the two cell membranes. At the time when the mid-body appears, the spindle bridge is always greatly con- stricted in the middle and consists then of a lesser number of fibers than during its earlier stages. The mid-body appears to consist of a thickening or a concentration of the cytoplasm of the fiber at one certain point. Thus there is either one thick granule (Fig. 62) for each one of the thicker fibers, or there is one granule connecting several of the fibers (Fig. 63). A solid plate is never formed, and the individual granules of the mid- body can always be recognized after proper differentiation. In Fig. 62 we see how some of the fibers have become beaded along their whole length, and we can easily understand that the individual granules of the mid-body can consist of a con- centration of the granules of the fibers. If this is a correct explanation of the formation of the mid-body, then it is also likely that the nature of the mid-body is the same as that of the granular nodes of the individual fibers; that is, a larger storehouse for the cytoplasm of the fibers from which the fibers may quickly draw a supply when, through the separation of the cells, the spindle bridge is suddenly extended. The mid-body would thus prevent the bursting of the spindle bridge at times of unusual strain. Again when the spindle is compressed on account of the pressure exerted by the retractile fibers, the cytoplasm of the fibers can be quickly concentrated in the mid- body, there to be stored for further use. This theory of the mid-body is supported by the fact that in extended spindle bridges (Figs. 13, 17, 32, 109) the mid-body is always absent, evidently then having been used up by the extension of the spindle bridge. V. VARIETIES OF CELLS. Polymorphous Spermatogonia. As polymorphous spermatogonia I designate the largest kind of spermatogonia which, during their resting stage, possess deeply folded or polymorphous nuclei. These polymorphous No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 53 nuclei occur only in the earliest resting stages, but as there are no other cells possessing similar nuclei, no difficulty will be encountered in recognizing the cells. In testes from ani- mals killed in June and July there are comparatively few poly- morphous nuclei, frequently only one or two, seldom more than three or four, in each section of a pocket of cells. The other cells in the pocket are mostly spermatogonia with round nuclei, neaeente eo OR} fe ° ° c ° ° A polymorphous spermatogonium in the ‘‘ perfect resting stage.” The form of the nucleus allows the most perfect metabolism. Numerous chromioles are connected by a thread of chromo- plasm. A network of linosomes is partially indicated, the individual granules being con- nected by linopodia. 5. Round Cell ee JSpermato- eG gonia. par 2S > 6.4 2 > > & ° ——— eat aa Las) LY) ———— SS SS = SS SS Sa —= ——— —=> SS © \ 9. Spermatozoa. Explanation of the Diagram of the Various Generations of Cells in the Testes of Batra- choseps. 1. Polymorphous spermatogonia, with polymorphous nucleus, somatic mitosis with twenty-four chromosomes. The daughter-cells of these spermatogonia constitute the following generations 2-s. 2. Spermatogonia with round nucleus, somatic mitosis with twenty-four chromosomes. The daughter-cells of the polymorphous spermatogonia. There are several generations in rapid succes- sion, and apparently all alike. These generations are as follows: 3. Spermatogonia with round nucleus similar to No. 2. 4. Spermatogonia with round nucleus similar to No. 2. 5. Spermatogonia with round nucleus similar to No. 2. 6. Auxocytes, the daughter-cells of the last generation of round nucleated spermatogonia. The change which caused a mitosis with twelve chromosomes takes place in the resting stage. The auxo- cytes are characterized by twelve chromosomes, a bouquet stage, anda heterotypic mitosis. Equa- tion division. Fiber cones after the anaphase. One generation. 7. Spermatocytes with twelve chromosomes, the daughter-cells of the auxocytes. Characterized by the absence of a bouquet stage. Fiber cones with certainty only in the pe homoeotypic mitosis and equation division. One generation only. The daughter-cells of the spermatocytes are the spermatids. . 8. Spermatids. g. Spermatozoa. 62 EISEN. [Vox. XVII. somic process in arranging the chromosomes on the central spindle and in pulling them apart. But the process takes no active part in the formation of the chromosomes. The chromosomic process again, as the name implies, refers only to the nucleus and to the formation of chromomeres, chromosomes, the splitting of the chromioles, and the manipu- lation of the linin. The united object of the two processes is to properly separate and divide the chromioles. The chromo- somic process is presided over by the chromoplasts and the linoplasts, just as the radiosomic process is presided over by the archosome and the accessory archosomes. These two processes are carried through about seven gen- erations of cells, four of which belong to the polymorphous spermatogonia, and one each to the auxocytes, the spermato- cytes, and the spermatids. These five classes of cells divide according to three distinct kinds of mitosis: the polymorphous spermatogonia by somatic or regular mitosis (not by amitotic division), the auxocytes by heterotypic mitosis, the spermato- cytes by homoeotypic mitosis. As regards the mitosis of the spermatids I am uncertain, not yet having properly studied it. I have, however, seen mitotic figures among the spermatids, hence my supposition that we may possibly have among the sper- matids two generations. Only the prophases of the somatic mitosis will be treated of in detail in this paper. One of the most interesting parts of the chromosomic process is the change of the mitosis with twenty-four chromosomes to the mitosis with twelve chromosomes. This change seems to take place in the imperfect resting stage of the auxocyte and to be guided by the chromoplast. In the spermatogonia the chromoplast projects finally twenty-four leaders, while in the auxocytes the chromoplasts project finally only twelve leaders, which latter change into chromosomes. As regards the reason why this change is made and the particulars of how it is made, we have no satisfactory observations upon which to base any theories. Whether the reduction is the result of the chromo- somic process alone, or the effect of a combination of the two processes, is at present not quite clear; there is, however, one fact, that would seem to indicate that the radiosomic process, No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 63 to some extent at least, influences the formation of the leaders. I refer to the fact that at the very beginning of the bouquet stage those ends of the leaders which are not connected with these chromoplasts point to the granosphere, and they not only point to the sphere, but they actually cover a surface which is just as wide as the granosphere, this fact determining the bou- quet form. Just before the formation of the bouquet stage the chromoplasts are situated in that part of the nucleus which is nearest to the granosphere, but as the leaders are becoming more defined, the chromoplasts move away from the spheres to the opposite end of the nucleus, leaving the ends of the leaders resting on that part of the nuclear wall nearest the spheres. The ends of the leaders are so placed that at the point of con- tact with the membrane they are closer together than a short distance from it. If there thus exists a real influence on the leaders from the spheres, this influence must be passing through the nuclear membrane, which at this time, and for some time to come, remains intact. The reduction in the number of chromo- somes is certainly not performed by any rays or fibers, as these have not yet penetrated the nuclear wall. The Radiosomic Process, or the Evolution of the Spheres, Spindles, Fibers, Archosome, and Accessory Archosomes. The radiosomic process begins in the polymorphous sper- matogonia with the formation of the granosphere (Figs. 1-8). The cytoplasm proper is then in the form of a very thin shell on all sides surrounding the polymorphous nucleus. In this cyto- plasmic envelop a denser area appears (Fig. 2), which is at first homogeneous, but which later on differentiates into smaller isolated areas or vacuoles, surrounded by denser staining granules. At the same time an outer zone is forming of much larger dimensions, but of less consistency. The outer zone is the plasmosphere, and the inner one is the granosphere. While this has taken place in the spheres, the cytoplasm has spread over the larger part of the cell, having lost its thin shell-like form. Already, with the first appearance of the granosphere, there appears also in the cytoplasm one or more 64 ELSEN. [VoL. XVII. dark-staining bodies, one of which enters the granosphere and becomes the archosome, while the others remain as accessory archosomes. The archosome, as well as the accessory archo- somes, divides. The two-centrioled archosome soon rises above the granosphere and carries with it a part of that sphere (Fig. 35). Metaplasmic secretions have also appeared among the granules of the two spheres. The central spindle is formed by the separation of the two centrioles and by the supplying of material from the granosphere to the rays formed between the two archosomes. The polar rays, or fibers, and the mantle fibers are formed at about the same time. The contractile fibers are formed, partly at least, of a different material and are from the beginning of different structure, being beaded and of a con- tractile nature. The relative position of the central spindle and the nucleus is alone dependent on the relative position of the granosphere and the central spindle. The central spindle is always so situated that a plane passing through its equator also passes through the granosphere. Numerous accessory archosomes have formed which probably assist in the forma- tion of the contractile fibers. There is always one, sometimes two archosomes at each pole of the central spindle. Before the poles of the central spindle have reached the opposite sides of the nucleus, the nuclear membrane has been destroyed by rays of the mantle fibers (Figs. 41-47). Shortly afterwards the chromosomes are thrown on the central spindle and taken hold of by the contractile fibers. After the anaphase or mitosis is over, a cytoplasmic membrane is formed around the nucleus, and as this membrane is being pulled away by a set of fiber cones a vacuole is formed around the nucleus in which the nucleus has ample room to develop. These fiber cones are often numerous and as high as seventeen in a single cell. The cones are formed as follows. The accessory archosomes ap- pear on the cytoplasmic membrane, and fibers are projected in various directions on the membrane. The archosomes then rise above the membrane, pulling with them the fibers, which, however, remain attached to the membrane with their distal ends. The cones rise so far as to project high above the regular circumference of the cell (Fig. 69). This formation No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 65 of fiber cones takes place only in the auxocytes. A new set of fibers appear radiating from the poles of the spindles after they have passed down through the ring-like nuclei of the auxocyte. The object of these fibers is to pull the daughter- cells apart. The latter part of the radiosomic process consists in the reconstitution of the spheres and the reassumption of its original position by the nucleus. With this the radiosomic process can be considered finished in the auxocyte. In the spermatocyte it commences in a different manner. Instead of a central spindle being formed by the separation of the two halves of the archosome, it is, at least in the majority of instances, formed by the junction of two opposite spindle cones. The fibers of these cones dissolve the nuclear membrane and by approaching each other form the central spindle. This part of the radiosomic process I have, from want of sufficient mate- rial, been unable to study as carefully as that which takes place in the auxocytes. I do not deny that a central spindle may be formed in the same manner as in the auxocyte, but I have failed to find any evidence of such a formation. There is, however, undoubted evidence that a central spindle is actually formed by two opposite fiber cones which, receding from the cell wall, meet in such a way as to form the spindle. The other parts of the process are the same as that which takes place in the auxocytes. To the radiosomic process must also be referred the forma- tion of the new cell walls which separate the two daughter-cells and the pulling apart of the two new cells. The new cell wall between the two daughter-cells is formed in the following way. Already during the metaphase (Fig. 53) the plasmosphere has scattered, and many of its granules and secretions have become located along the equator of the cell. As the anaphase progresses, this accumulation of plasmospheric granula becomes more prominent along the line of the future cell wall. The plasmospheric granula are never distributed evenly along the equator, but always in isolated rounded groups (Figs. 54-56). In the figures referred to, the plasmo- spheric fragments are stained deeper red than any other part 66 EISEN. [VoL. XVII. of the cytoplasm. Frequently the plasmosphere is seen on one side of the cell (Fig. 55), and not on the other, and it seems that this is rather the rule than the exception. The con- traction of the cell wall commences at the place where the plasmospheric fragments touch the equator. Just previous to this contraction the plasmosphere has at that point divided in two in such a way that one-half of it lies immediately above the equator, while the other half lies under it, that is, one-half in each of the future daughter-cells (Figs. 55, 56). In the mean time the mantle fibers have become connected by their ends with the individual granules of the plasmospheric frag- ments, the other ends of the fibers being attached to the spindle pole. The contraction of the cell wall appears to be accomplished directly by the contraction of the mantle fibers. At a stage a little more advanced the ends of the mantle fibers, which were at first attached to the spindle poles, become attached to the cytoplasmic membrane around the nucleus (Fig. 61). Another set of fibers have also made their appear- ance in the vicinity of the mantle fibers. These fibers, for which I propose the name of retractile fibers, connect the arch- osome at the spindle pole, which has now passed through the nucleus, with individual granules of the plasmosphere (Figs. 59-61), as well as with purely cytoplasmic granules along the equator. While this contraction is taking place in the equator of the old cell wall, a change has also appeared in the equator of the central spindle. Instead of being comparatively dense and even, larger and smaller vacuoles have formed (Figs. 56, 57). These vacuoles are at first diamond-shaped, with their longer axis parallel to the spindle axis; but later on they are drawn out sideways, in the plane of the equator, while at the same time plasmospheric granules appear along their mar- gins. The new cell walls appear to be secreted out from these granules along a double line of parallel walls of vacuoles. As soon as the two parallel cell walls have formed they are sepa- rated by the retractile fibers of the spindle cones. There are thus four processes cooperating in the formation of the new cell wall: the plasmospheric granules are placed along the equator of the cell; the central spindle is becoming vacuoled Nos SPERMATOGENESIS OF BATRACHOSEPS. 67 in the equatorial plane, and the vacuoles are drawn out side- ways; a new membrane is secreted along the walls of the vacuoles from the plasmospheric granules; the two walls are pulled apart first by the mantle fibers, later on by the retractile fibers of the spindle cones. A few minor points of this process are of sufficient interest to be noted. One of these is that in the beginning the con- traction sinus (Figs. 56, 61) in the cell wall is rounded, while later on (Figs. 50, 60) it is very acute, thus indicating that, to begin with, there is only a contraction of the old cell wall, which, of course, is single, but that later on there is an actual pulling apart of two parallel walls. Another point is that the first contraction never takes place all around the cell at the same time, but always, or perhaps generally, along one side first. This may either be due to a want of sufficient plasmo- sphere, or to an effort to keep the cell more steady, or perhaps to both. It will be seen that the central spindle is the pivot upon which most all of this pressure is applied, and that the simultaneous passing of the central-spindle poles through the umbrella-shaped nuclei can be accounted for by the pressure exerted by the retractile fibers on the spindle poles, coupled with a contraction of the central-spindle fibers themselves. The Chromosomic Process. The Formation of the Chromioles ento Chromomeres and Chromosomes. As has already been stated, this process is carried along inde- pendently of the radiosomic process, but parallel to it. It takes place in the nucleus principally before the nuclear mem- brane has been dissolved, and is, during all this time, not influ- enced by the action of the archosomes or by the accessory archosomes. It is undoubtedly presided over by the chromo- plasts and the linoplasts. It begins in the perfect resting stage of the polymorphous spermatogonia with the formation of the leaders, and is thence carried on through the different varieties of cells without any cessation or perfect rest until the spermatozoa are formed. The whole chromosomic process can conveniently be divided into the following principal subdivisions: 68 EISEN. [Vou. XVII. Formation of twenty-four leaders in the polymorphous sper- matogonia. Somatic mitosis of the same. Formation of twelve leaders in the auxocytes. Longitudinal splitting of the spireme segments or leaders. Fics. a.-g. represent a broken series of leaders illustrating the formation of the leader and the chromosome. a.— Isolated row of chromioles surrounded by chromoplasm and suspended in a network of linosomes; 4. —Chromoplast with twelve leaders of chromioles. From the imperfect resting stage of the polymorphous spermatogonium ; c. — Chromoplast with five leaders. Each leader is made up of chromomeres, and each chromomere consists of three or more chromioles surrounded by chromoplasm. A network of linosomes between the chromomeres; d.— Three chromomeres, each with six chromioles surrounded by a chromoplasm and suspended in a network of linosomes; e.— A bretzel chromosome con- taining chromioles and two chromoplasts with endochromatic granules; 7— A chromo- some from the metaphase. It contains thirty-six chromioles and a terminal chromoplast with an endochromatic granule ; 2. — Part of a chromosome from the spermatocyte. Contraction of the separated halves of the leaders into chro- mosomes. Equation division of the chromosomes by heterotypic mitosis. Confluence of the chromosomes. No: 1: ] SPERMATOGENESIS OF BATRACHOSEPS. 69 Reconstitution of the chromosomes and a period of growth. Equation division of the chromosomes by homoeotypic mitosis. . Confluence of the chromosomes. Reconstitution of the chromosomes and a period of growth. Some of these stages are more composite than others and include several more or less distinct processes, all of which will now be considered together. For convenience’ sake and for greater clearness I have for each one of them adopted distinct names, under which they will now be referred to. As these stages also mark the principal stages in the evolution of the nucleus, the same names will be used for the various stages in the evolution of the nucleus. It must be remarked that while the radiosomic process in a general way goes hand in hand with the chromosomic process, the various substages of each do not always meet in the same nodes. Thus, for instance, while generally the contraction of the cell wall begins before the confluent umbrella stage in the auxocyte, it may also be delayed until the end of this stage. This shows even more conclusively that the two processes are, to a great extent, independent of each other, and that they only meet in order to perform jointly the mitosis of the chromosomes. A. The Chromosomic Process in the Polymorphous Spermatogonta. Perfect Resting Stage.—In this stage the chromioles are spread over the polymorphous nucleus and generally separated one from the other, though they are connected by linin threads, forming winding lines all through the nucleus. These lines are not yet connected with the chromoplasts, which lie free in vacuoles, only surrounded by linin. There are from one to several linoplasts (Figs. 1-3). Imperfect Resting Stage.— The threads of linin with the chromioles connect with the chromoplasts and form leaders. The chromioles begin more and more to approach each other, and to form small chromomeres with two or three chromioles in each (Figs. 8, 9). 7O EISEN, [VoL. XVII. The various phases of mitosis now follow according to the somatic process. There are twenty-four chromosomes on the central spindle, and the result of the mitosis is also twenty-four chromosomes carried to each daughter-nucleus. These become confluent, after which the nucleus enters a stage of growth. In this stage the appearance of the nucleus is very much the same as in the imperfect stage of rest, just before the beginning of the mitosis. This stage also marks the be- ginning of the auxocyte. There are several generations, but only one with polymorphous nuclei, the others having round nuclei. B. The Chromosomic Process in the Auxocytes. A Stage of Growth, during which the daughter-cell of the former mitosis increases in size and finally reaches an imper- fect resting stage. In this stage the leaders are formed and their ends connected with the chromoplasts, of which there are two or more resulting from division of the original chromo- plast. The chromioles are in groups of three, and each group is surrounded by a film of chromoplasm. The leaders are thus made up of numerous small chromomeres, connected by a linin string and suspended in a linin network. There are several linoplasts of various sizes (Figs. 10, 11). The two spheres are perfectly formed; a perfect archosome with two centrioles is generally present in the granosphere. Bouquet Stage with Twisted Leaders. —In this stage the leaders have contracted to about one and one-third the diam- eter of the nucleus. They are bent and somewhat twisted, but their arrangement is still so regular as to present the appear- ance of a bouquet. One end of each leader in the bouquet is attached to the chromoplast, of which at this stage there is one or a few. There are many chromomeres, several linoplasts, and a perfect network of linin. The ends of the leaders, or spireme segments, point generally directly towards the spheres. This is, however, not always the case, as sometimes the narrow part of the bouquet points upwards or even in an opposite direc- tion to the spheres. It appears, therefore, that the nucleus in the bouquet stages regularly revolves in such a way that the No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. px spheres remain in the equator. This revolving of the nucleus is characteristic of all the bouquet stages (Fig. 12). Perfect Bouquet Stage. — The leaders have contracted more, and their length is now only a trifle longer than the diameter of the nucleus. The chromoplasts have divided and the lead- ers have, to a great extent, separated. Seldom more than two leaders are connected by a chromoplast. The chromomeres during this stage diminish in number, two and two fusing together, so that each one finally has six chromioles instead of three, as previously. The divided chromoplasts are recogniz- able by the endochromatic granules (Figs. 13, 14). Bouquet with Split Segments. — This is the last of the bouquet stages, in which the chromomeres are twelve in each ‘leader. Each chromomere splits in two longitudinally. Gen- erally, two leaders are connected by a dividing chromoplast. One or more linoplasts (Fig. 15). Separated Segments. — The bouquet stage has been passed, the leaders have spread apart, and their free ends do not any more point to the spheres but stretch out in various directions. Not only the chromomeres, but the whole leader is divided, and the separated halves twist around each other, only remain- ing here and there connected through the non-division of cer- tain chromomeres. Generally, only two leaders are connected by one dividing chromoplast. Several linoplasts (Figs. 16-23). Angular Segments. — The separated leaders have now both contracted and straightened out in such a way as to form even and nearly straight rods which cross each other at regular intervals. The chromomeres are not as distinct as in previous stages. The rods which represent chromosomes are connected, as formerly, with chromoplasts. The linoplasts have all dis- solved, and the linin network has become partly disarranged, its function evidently now having ceased for the time being. The exact process by which this straightening out of the chro- mosomes has been accomplished is difficult to explain, but the object is evidently to untwist the segments and to separate them from each other. This straightening out could not be accomplished without an almost perfect fusion of the chromo- meres (Fig. 34). 72 EISEN. [Vor. XVII. Irregular Bretzel. — The leaders or spireme segments have contracted and formed bretzel-shaped chromosomes, two or more of which are connected by chromoplasts. The chromo- meres are reconstituting into six larger chromomeres in every chromosome. The linin network is becoming more and more disintegrated, separating itself from the chromosomes and accumulating in a different part of the cell. During this stage the central spindle is forming, and at the end of the stage the nuclear membrane is being dissolved by the mantle fibers (Figs. 35-46). Bretzel Metaphase. — The bretzel-shaped chromosomes have separated from each other, a part of a chromoplast remaining attached to each one of them, but no two are connected together. The nuclear membrane is entirely dissolved; the linin granules have mixed with the cytoplasm, and the chro- mosomes have been thrown on the central spindle and are at the end of this stage arranged in a ring on the equator of the spindle (Figs. 47-53). V-shaped Anaphase.— The equation division of the chromo- somes has taken place, and the daughter-chromosomes have been pulled towards the poles in the form of V’’s (Figs. 54-56) by the contractile fibers. The chromoplast remains stationary at the end of one of the arms of the chromosome. Confluent Umbrella Stage.— The chromosomes have con- tinued to contract and fuse together until they have so com- pletely fused into an umbrella-shaped, ring-like mass that the individual chromosomes are no more definable. In this stage the endochromatic granules become distinct in the umbrella, indicating the presence of the chromoplasts (Figs. 57-61). One of the objects of this stage is to allow the chromoplasts to move from the end of the chromosome to its angle. Chrysanthemum Stage.—In this stage the chromosomes begin to reappear, and they are at that time bunched together and the whole nucleus has the form of a chrysanthemum flower, the open part being towards the daughter-cell. The chromo- plasts appear from the start at the angle of the chromosomic arms. The cytoplasmic membrane formed around the nucleus is being more and more pulled away, giving the nucleus No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 73 the opportunity for a stage of growth, enabling it to increase to about twice its former size. In this stage the daughter-cells become entirely separated, after which they are to be termed ‘“‘spermatocytes.”’ If we consider the spermato- cyte to begin with the reappearance of the chromosomes, then this chrysanthemum stage should be counted as belonging to the spermatocyte and not to the auxocyte. If we date the appearance of the auxocyte from the stage of growth, then we ought also to date the appearance of the spermatocyte from the stage of growth of the nucleus. C. The Chromosomic Process in the Spermatocytes. The Chrysanthemum Stage, in which the chromosomes have the form of staples and horseshoes. This stage is similar to the one described as the last one of the previous cell genera- tion (Figs. 62-70). Numerous fiber cones. Checkerboard Stage.—The staple-shaped chromosomes of the previous stage have grown and become elongated, and the chromomeres have become so separated as to be spread over the nucleus almost as the squares on a checkerboard (Figs. 71-82). In the first half of this stage the fiber cones are dis- appearing, either completely or with the exception of two, which later join to form the new central spindle. The spheres are being reconstituted during this stage. Contraction Stage.— The scattered chromomeres again ap- proach each other and form strongly beaded chromosomes. The nuclear membrane is being dissolved by the fiber cones or by the fibers of the new central spindle (Figs. 83-86). Angular Chromosomes.—In this stage the chromosomes straighten out and become narrower, cross each other at vari- ous angles, and the chromomeres become so fused that they can hardly be distinguished one from the other (Fig. 87). Knotted Chromosomes. — The chromosomes have separated from each other to a lesser or greater extent and are thrown in a knot in the center of the cell. The chromosomes do not yet have the regular and finished form of V’’s (Figs. 88-91, 94-97). V-Metaphase. —The chromosomes are in the shape of per- fect V’’s and are as such thrown on the equator of the central 74 EISEN. [VoL. XVII. spindle. The V’’s are split and the mitosis is made by an equa- tion division, the V’’s being exactly halved throughout their length (Figs. 99-101). V-shaped Anaphase. — The chromosomes are at the poles in the form of contracting l’’s (Figs. 192, 193). Confluent Umbrella Stage. — The chromosomes have be- come entirely confluent. This phase corresponds entirely to the confluent umbrella phase of the auxocytes. It possesses the same general characteristics as that phase, but there are no fiber cones formed (at least not to the same extent as in that phase, nor are they as plain or as pronounced, if they actually exist). The same kind of cytoplasmic membrane is formed around the nucleus which enters a reconstitution stage, just as in the auxocytes. From a want of sufficient material this stage has not been thoroughly studied (Figs. 104-108). Transition Chrysanthemum Stage, in which the nucleus is reconstituted through a stage of growth, the chromosomes passing through a chrysanthemum stage into a checker- board stage, as in the auxocyte. This is the last stage in the life cycle of the spermatocyte and also the first stage of the spermatid. As I expect to make the spermatids and their evolution into spermatozoa the subject of a special paper, I give here only a single figure of a perfectly formed spermatid (Fig. 109). As regards the various stages of the chromosomic mitosis of the auxocytes, I will only offer a few remarks. Accessory Archosomes. — All archosome-like bodies found in the cytoplasm, and which have the same structure as the true archosome, that is, consist of centriole, somosphere, and cen- trosphere. Siderophile granules of A. Bolles Lee. The acces- sory archosomes differ only from the archosome in function, the latter presiding over the formation of the spindle. They origi- nate from the archosome (Fig. 69). Alveolt. — Rounded or variously shaped vacuoles, surrounded by granules. They contain secretions of various kinds, accord- ing to the structure in which they are found. Angular Segments. — The spireme segments have con- tracted and straightened out, and have become of uniform thickness throughout (Fig. 34). Archosome or Spindle Archosome.— The perfectly developed archosome which guides the formation of the central spindle. It generally dwells in the granosphere when it is not situated at the pole of the spindle. It is composed of an outer centro- sphere, an inner somosphere, and one or more interior centri- oles. It is not an integral part of the granosphere. The archosome gives origin to the accessory archosomes by bud- ding. The granosphere and the plasmosphere are not parts of the archosome. The word “archosome”’ was first proposed by me in my paper on the Plasmocytes of Batrachoseps. Auxocytes. — This name was first proposed by A. Bolles Lee. The first maturation cells, the last generation of daughter-cells of the polymorphous spermatogonia. Only one generation. The mitosis is heterotypic with twelve chromosomes, and is charac- terized by the bouquet stage. Mitosis by equation division. The nucleus is never polymorphous. Bouquet Stage. — The spireme leaders have contracted and formed twelve segments of about equal size, one end of which is attached to the chromoplast, the other being free, and ending in the vicinity of the spheres, thus forming a figure resembling No. I.] SPERMATOGENESIS OF BATRACHOSEPS. gI a bouquet. This stage contains the three substages mentioned below (Figs. 12-15). Bouquet Stage with Twisted Segments.— The spireme seg- ments are about one-third longer than the diameter of the nucleus. Many small chromomeres (Fig. 12). Bouquet with Split Segments. — The chromomeres are dis- tinctly split, but are not yet separated (Fig. 15). Bretzel Stage. — The segments have the form of bretzels or twisted rings. These bretzel-shaped chromosomes may be more or less regular, and their ends may only overlap each other, or they may be actually grown together (Fig. 25). Central Spindle. — The primary spindle by which the archo- somes are united, and which form the center of the mitotic figure. It does not include the contractile fibers attached to the chromosomes, nor the mantle fibers. The spindle which connects the two poles (Hermann, Figs. 49-56). Centriole. —The innermost dark-staining granule or granules, situated in the center of the archosome, and also in the acces- sory archosome. It does not include the somosphere. Centrosome. — On account of the many and various defini- tions given by respective investigators, this name has recently been discarded by several investigators, among them by W. Flemming, who substitutes the word Centralkorper. But while we are told that this word expresses the same thing as the word “centriole,” we are yet at a loss to know if it includes the somo- sphere, or the somosphere and centrosphere. When the word “‘centrosome’’ is used in this paper, it is always left open and undecided whether we have before us an archosome or an acces- sory archosome. I use this word only to indicate a centriole surrounded by its somosphere. Centrosphere. — The more or less hyaline and indifferently stainable zone surrounding the somosphere and centriole, the outer sphere of the archosome, as well as of the accessory archosomes. It is sometimes amoeboid, sometimes again cir- cular or globular, with a perfectly even outline. It is princi- pally an organ of locomotion. Checkerboard Stage. — The second prophase of the sperma- tocyte. The chromomeres have separated and scattered over Q2 EISEN. [VoL. XVII. the nucleus, making it appear as a checkerboard. This is the principal stage of growth of the nucleus (Fig. 77). Chromatin, the darkly staining substance of the chromo- somes, applied without reference to any of the particular structures. Chromtioles. — The smallest visible organized parts of the chromosomes. Possibly the bearers of heredity. They are of constant form, size, and number in each typical and perfect chromosome. In the perfect resting stage of the auxoyctes, the chromioles are scattered free in the nucleus, and not col- lected in chromioles or chromosomes. There are typically thirty-six chromioles in every chromosome. Chromomeres.— Small aggregations of chromioles, surrounded by a film of chromoplasm. There are six chromomeres in each perfect chromosome. Chromoplasm. — The dark-staining plasma, which surrounds the chromioles, and which unites them into chromomeres and chromosomes. Also found in the chromoplasts. Chromoplasts. —One or more rounded and well-defined bodies, found in the nucleus, either free or attached to the leaders and the chromosomes. Chromoplasts guide the formation of the chromosomes, just as the archosomes guide the formation of the spindles. Variously named karyosome, net-knot, Netz- Knoten, nucleolus, etc. Chromosomes. — The contracted leaders, with six chromo- meres. There are twenty-four of these in the polymorphous spermatogonia, and twelve in the two maturation cells. Chromosomic Process. — One of the two independent pro- cesses, the formation of the chromomeres and the chromosomes from the chromioles and chromoplasm ; this process is presided over by the chromoplast. Chrysanthemum Stage.— The first prophase of the sperma- tocyte. The chromosomes have begun to reappear, forming a figure resembling a chrysanthemum flower (Fig. 67). Contractile Fibers. — Fibers directly connecting the chromo- somes with the somosphere and the centriole, and which thus penetrate the centrosphere. There are as many contractile fibers as there are chromosomes (Figs. I11I—I13). No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 93 Contraction Stage. — The third prophase of the spermato- cyte. The chromosomes have again contracted and assumed forms resembling staples or horseshoes (Fig. 83). Cyto-Microsomes. — The most minute visible granules of the cytosome, the granula of which the spheres and most of the fibers are constructed. Cytoplasm. — All the protoplasm in the cytosome. The pro- toplasm of the cell proper. Does not refer to the protoplasm of the archosome and the nucleus. Cytosome. — The part of the cell outside of the nucleus and the archosome. The two spheres are essential parts of the cytosome. Endochromatic Granules. — Highly refractive granules found in the chromoplasts and in the confluent stage of the nucleus. Probably food supply or stimulant for the chromioles. Fiber Cones. — Cones of fibers projecting from the accessory archosomes, and which make their appearance at the end of the anaphase. They sometimes elevate the cell membrane, forming large cones. The base of the cone is at first attached to the cytoplasmic membrane around the nucleus (Fig. 114). Granosphere. — The inner strongly granulated sphere, some- times called the attraction sphere. It stains more intensely than the other sphere, and it furnishes material for the central spindle. It is the favorite dwelling-place for the archosomes. Heterotypic Mitosis. — Mitosis, in which the chromosomes are thrown on the central spindle in the shape of bretzels or rings. The mitosis is by equation division. The mitosis of the auxocytes. Hlomoeotypic Mitosis. —The chromosomes are thrown on the spindle in the form of V’s. The mitosis of the sper- matocytes. Imperfect Resting Stage.—In this stage of the nucleus the leaders have formed, but there are no finished chromomeres, nor any chromosomes. This stage follows the last described stage. Is found in the polymorphous spermatogonia and in the auxocytes. Leaders or Spireme Segments. — Strings of chromoplasm and linin on which the chromioles are suspended, singly to begin 94 EISEN. [VoL. XVII. with, later on in twos and threes. There are as many leaders as there are to be chromosomes. The leaders condense into chromosomes. The leaders are connected with each other only by the chromoplasts. Linin Granules or Granula.— The smallest visible granules composing the linin network and threads. Also found free in the nucleus during the resting stage and after the prophases. Linin Network. — The congo-staining network supporting all the chromatin structures during the prophases. Linoplast. — One or more round bodies in the nucleus, staining like the linin and the cytoplasm. They supply the material for the linin network, when this is in rapid increase. Generally called true nucleolus. Linopodia.— The thread-like or bar-like projections from the individual granules of the cytoplasm, and from the linin and other granules of a similar nature. By these linopodia, the individual protoplasmic granules are able to adhere to each other and to form network or foams. These linopodia are retractile, very much like the pseudopodia of the amoeba, but they are more regular and even throughout their length. Mantle Fibers. — All fibers of the mitotic figure, which radi- ate from the outer margin of the centrosphere, and which sur- round the central spindle. The polar fibers and the contractile fibers are not included in the mantle fibers. Metaplasmic Secretions. — The various secretions confined in vacuoles of the spheres. Mid-Body. — A number of darkly staining granules, situ- ated on the fibers of the central spindle, at a place where the two daughter-cells separate. They are probably caused by a concentration of the cytoplasmic granules of the fibers, separated and only suspended by thin threads of linin (Fig. 64). Paracellular Bodies. — Bodies of various sizes and structure found between the cells. They are probably expelled centro- somes and particles of the spheres. Some are free, others are attached to the cells by threads of protoplasm. Parachromatic Granules. — Granules found in the nucleus during the resting stage and in the immediate vicinity of the No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 95 chromoplasts. Stain as the chromatin with the iron-haema- toxylin. Their nature is not known. Paralinin Granules. — Larger, deeper staining granules of unknown nature mixed in among the linin granules of the linin network. Paranucleolar Granules. — Dark-staining granules, forming a shell around the linoplast or true nucleolus. Paraplasmic Granula. — Granules of undetermined quality found in the cytoplasm. They are often difficult to distinguish from the centrosomes. Perfect Bouquet Stage.— The spireme segments are only slightly longer than the diameter of the nucleus. The seg- ments are more parallel (Fig. 14). Plasmosphere. — The outer, generally lighter staining of the two spheres of the cytosome. It surrounds the inner or grano- sphere, but is sometimes scattered. It furnishes material for the mantle fibers and for the nuclear membrane. Polar Fibers. — All fibers radiating from the outer margin of the centrosphere, and which extend in a direction opposite to that of the mantle fibers. Of the same general nature as the mantle fibers. Polymorphous Spermatogonia.— The largest spermatogonia with polymorphous nuclei during the resting stage, becom- ing less and less polymorphous, as the leaders are being formed. They divide by somatic mitosis, and possess twenty- four chromosomes. There are three or four generations, but only the first one of these contains polymorphous nuclei. Prophases. — All mitotic stages between the imperfect rest- ing stage and the perfect metaphase. The phases in which the chromomeres and the chromosomes are being formed, and their structure finished (Figs. 12-44). Radiosomic Process.—The evolution of the spheres, spindles, and fibers ; one of the two independent processes by which the mitosis of the cell is accomplished. This process is presided over by the archosomes and the accessory archosomes. Retractile Fibers. — A set of fibers radiating from the poles of the central spindle, when the poles have descended through the ring-like nuclei of the daughter-cells. They end on or 96 EISEN. [VoL. XVII. near the new membrane forming between the two cells, their function being to separate the two cells (Figs. 68-70). Ring Stage.— The last of the bretzel stage in which the chromosomes are ring-shaped (Fig. 25, 7.f.¢.). Separated Segments. — The chromomeres and the segments have separated, and the latter have twisted around each other, and often cross each other in various directions (Figs. 16, 17). Somatic Mitosis. — Mitosis, with twenty-four chromosomes, dividing in the same way as the somatic cells. The mitosis of the polymorphous spermatogonia. Somosphere. —The thin, dark-staining zone nearest surround- ing the centriole, and situated interior to the centrosphere. It has sometimes the form of a narrow, even band or thread. Spermatids. — The daughter-cells resulting from the mitosis of the spermatocytes. Possibly two generations, the last of which change directly into spermatozoa. Spermatocytes. —The second maturation cells. The daughter- cells of the auxocytes. Mitosis homoeotypic and by equation division, with twelve chromosomes. One generation only. Chromosomes are placed on the spindle in the form of V’s. Spindle Cones. — The cones formed of the retractile fibers around the poles of the central spindle, when the latter has been pulled through the ring-like nuclei of the daughter-cells (Fig. 114). Spireme Segments or Leaders. — Strings of chromoplasm on which are suspended the chromioles. There are as many spireme segments as there are to be chromosomes. The spi- reme segments do not form a single continuous thread, but are individually separated. Umbrella Stage.—The chromosomes in the amphiaster or anaphase have become confluent, and formed an umbrella-like body, in which the individual chromosomes cannot be distin- guished as such (Figs. 58-61). V-stage, in which the chromosomes have the shape of V’’s, the apex of which is attached to the spindle. Includes a meta- phase and an anaphase (Fig. 120). CALIFORNIA ACADEMY OF SCIENCES, San Francisco, California, April 26, 1898. No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 97 XI) LITERATURE, '95 ALTMANN, R. Ueber Granula und Intergranularsubstanzen. Arch. Jf. Anat. u. Phys., Anat. Abth. '96 ALTMANN, R. Ueber das Wesentliche in der Zelle. Arch. f. Anat. u. Phys., Anat. Abth. 96 AUERBACH, L. Untersuchungen tiber die Spermatogenese von Palu- dina vivipara. /enatsche Zettschr. f. Naturw. Bd. xxx, N.F. xxiii. '96-'97 BENDA, C. Neuere Mitteilungen iiber die Histogenese d. Sauge- tier-Spermatozoen. Verh. d. Phys. Gesellsch. Berlin. '83 BENEDEN, Ep. VAN. 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Neue Untersuchungen iiber die Centralkérper und ihre Beziehungen zum Kern und Zellenprotoplasma. Arch. f. mikr. Anat. Bad. xliii. 96 HENNEGUY, L. F. Lecons sur lacellule. Paris. ‘91 HERMANN, F. Beitrag zur Lehre von der Entstehung der karyokine- tischen Spindel. Avch. f. mikr. Anat. Bd. xxxvii. '97 HERMANN, F. Beitrage zur Kentniss der Spermatogenese. Arch. f. mtkr. Anat. Bd. 1. No. "75 '98 Bout oa 96 '97 Te] SPERMATOGENESIS OF BATRACHOSEPS. 99 LA VALETTE DE ST. GEORGE. Die Spermatogenese bei den Am- phibien. Arch. f. mikr. Anat. Bad. xii. LENHOSSEK, M. von. Untersuchungen uber Spermatogenese. Avrch. fj. mtkr. Anat. u. Entwicklungsgesch. Bd. li, Heft 2. MEVES, F. Ueber amitotische Kerntheilung in den Spermatogonien des Salamanders und Verhalten der Attractionssphare bei derselben. Anat. Anzeiger. 4. Jahrg. MEvEs, F. Ueber eine Metamorphose der Attractionssphare in den Spermatogonien von Salamandra maculosa. Arch. f. mikr. Anat. Bd. xliv. MeEvEs, F. Ueber die Entwickelung der mannlichen Geschlechts- zellen von Salamandra maculosa. Arch. f. mikr. Anat. Bd. xlviii. MeEvEs, F. Ueber Structur und Histogenese der Samenfaden von Salamandra maculosa. Arch. f. mikr. Anat. Bd. 1. ‘97a MEVES, F. Zellteilung. Wiesbaden. 93 195 ‘OT oT 96 '93 ioe 95 96 94 7 95 96 Moore, J. E. S. On the Relationship and Réle of the Archoplasm during Mitosis in Larval Salamander. Quart. Journ. Micr. Sct. Vol. xxxiv. Moore, J. E. S. On the Structural Changes in the Reproductive Cells during the Spermatogenesis of Elasmobranchs. Qvart. Journ. Micr. Sct. Vol. xxxviii. NIESSING, CARL. Die Betheiligung von Centralkérper und Sphiare am Aufbau des Samenfadens bei Séugenthieren. Arch. f. Anat. u. Entwicklungsgesch. Bd. \xxxiv. OsTERHOUT, W. J. V. Ueber Entstehung der karyokinetischen Spindel bei Equisetum. /ahrd. f. wiss. Bot. Bd. xxx. PLATO, JULIUS. Die interstitiellen Zellen des Hodens und ihre physi- ologische Bedeutung. Arch. f. mikr. Anat. u. Entwicklungsgesch. Bd. xlviii, Taf. XII. RATH, O. von. Zur Kenntniss der Spermatogenese von Salamandra maculosa. Zettschr. f. wiss. Zool. Bad. Ivii. RAwitz, B. Centrosoma und Attractionssphiare in der ruhenden Zelle des Salamanderhodens. Arch. f. mikr. Anat. Bad. xliv. Rawitz, B. Ueber den Einfluss der Osmiumsaure auf die Erhaltung der Kernstructuren. Anat. Anzeiger. Bd. x. Rawitz, B. Untersuchungen iiber Zellteilung. I. Das Verhalten der Attraktionsphare bei der Einleitung der Teilung der Spermatocyten von Salamandra maculosa. Arch. f. mikr. Anat. Bd. xlvi. REINKE, Fr. Zellstudien. Theil II]. Arch. f. mikr. Anat. Bd. xliv. SCHLATER, GusTAv. Zur Biologie der Bacterien. Bzol. Centralbl. Bd. xvii, Nr. 23. WILson, Epm. B. Archoplasm, Centrosome, and Chromatin in the Sea-urchin Egg. Journ. of Morph. Vol. xi. WILson, Epm. B. The Cell in Development and Inheritance. New York. 100 EISEN. [VoL. XVII. XII. EXPLANATION OF THE FIGURES. PLATES I~XIV, FIGs. 1-122. General Remarks. — All the figures have been drawn to the same scale projec- tion on the working table, by the aid of a Griinow drawing camera and with a Zeiss Apochromat, 3mm., Ap. I, 40, Oc. 18. The details were studied with a Zeiss Apochromat, 2 mm., Ap. I, 40, Oc. 12, the magnification thus being in both instances about 1500. An achromatic oil-immersion substage condenser was used for all detail work, and it was always supplemented by an achromatic light- filter as described under the heading of methods. A few of the figures, as stated in the text, have been drawn from Oc. 18, and with 2 mm. Objective. The stain- ing, with the exception of a few, has been the same for all the sections: iron- haematoxylin, with after-staining with congo. A few preparations were stained with congo-thionin-ruthenium red. The sections were cut about 5 mw thick and affixed to the slides by the alcohol method. All the figures are from the testes cells of Batrachoseps attenuatus Esch. Fixative exclusively iridium-chloride-acetic. The figures have principally been arranged according to the serial development of the nucleus, and not according to the development of the spheres and the spindle. In the later stages of the spermatocytes the figures have been partly arranged according to the development of the spindle. The figures in the text are strongly diagrammatic. Large Polymorphous Spermatogonia (figs. 7-9). Fic. 1. Large polymorphous spermatogonium, perfect resting stage. The large black body is the chromoplast surrounded by filaments of linin stained red. The chromoplast contains several highly refractive endochromatic granules. The large red body is the linoplast. The small granules, of uniform size and dark color, are the chromioles. The lighter stained granules are partly chromioles, partly linin granules, all of which are suspended in the linin network. A number of parachromatic granules are seen around the chromoplast. The cytoplasm has the form of a thin hollow shell surrounding the much folded nucleus. Two cen- trosomes in the cytoplasm. Remains of, or the beginning of, a granosphere at the top of the cytoplasmic shell. The dark-staining granules which form a shell around the linoplast are the paranucleolar granules. Fic. 2. Large polymorphous spermatogonium, perfect resting stage; the chro- moplast is larger and divided in two nearly equal parts, and is surrounded by an aster of linin threads of even length; at the tips of the threads are seen more dis- tinct linin granules. The granosphere is being reconstructed at the upper end of the nucleus, but in the cytoplasm. No centrosomes visible. A large lino- plast with paranucleolar granules. FIG. 3. Polymorphous spermatogonium in a more advanced stage than Figs. 1 and 2, but still in the resting stage. The chromioles, which are strung on threads of linin and chromoplasm, are being drawn towards the chromoplast, the leaders thus beginning to form. Two linoplasts of unequal size stained red. The nucleus is less polymorphous than in Figs. 1 and 2. The cytoplasmic granules are more scattered, forming a more extended and less ring-shaped cyto- some. Centrosome in the granosphere. Fic. 3 4. Detail of the granular reticulum or network of the linin. PLS. Journal of Morphology. Vol.XVu POT ra, oa * iia oh of? ee tea hn! .f oe id ieee why rr ae ‘ PRY AS 22 . Vig, %e se Sete iy = a 7 ‘Lith Werner & Winter Frankfore?M. Spermatogenesis of Batrachoseps. - Journal of Morphology. Vol.XVi. 14. Spermatogenesis of Batrachoseps. Pl. ll. Vol. XV Journal of Morphology. 2ps. Batrachose of s rmatogenes!i Ss pe No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. IOI Fics. 4 and 5 represent two successive sections of one polymorphous sper- matogonium in the resting stage. The nucleus is more contracted, with fewer folds. Two linoplasts. The chromioles are being drawn into the leaders and united into chromomeres. The spheres are being reconstituted, the granular zone being the granosphere. An archosome is seen in Fig. 5. Fics. 6 and 7. Two detail figures of polymorphous spermatogonia with fully reconstituted spheres, each with centrosomes. The nuclei are more advanced than in Figs. 4 and 5. In Fig. 7 are seen several accessory archosomes, each surrounded by a centrosphere. In each cell is a large linoplast. The nuclear network is merely sketched in and not carried out in detail. Fic. 8. A large polymorphous spermatogonium in a more advanced stage of development, in the imperfect resting stage. The nucleus has changed from poly- morphous to globular. The largest dark body is the chromoplast, the smaller one is probably a linoplast. Many distinct leaders have been formed, and are now connected by a network of chromioles and chromomeres. The spheres have been almost perfectly reconstituted, consisting now of an inner granosphere and an outer plasmosphere, an archosome with two centrioles, and several accessory archosomes, the latter scattered in the cytoplasm. Fic. 9. A large polymorphous spermatogonium, but in which the nucleus has lost its folded or polymorphous nature, being now at the end of the resting stage and just entering the prophases of mitosis. Between this cell and the one figured in 10 there is not only a whole somatic mitosis, but at least three or four genera- tions of round nucleated spermatogonia, all dividing by somatic mitosis, and with twenty-four chromosomeseach. The last of these generations gives rise to smaller oblong cells, which pass through a stage of growth and then constitute the first or imperfect resting stage of the auxocytes. In Fig. 9 there is seen a large lino- plast, three chromoplasts, with endochromatic granules. Leaders are séen to emanate from the chromoplasts. The spheres are not quite reconstituted. In the center is an archosome with two centrioles. Several accessory archosomes in the cytoplasm. The plasmosphere is starlike, the granosphere rounded and cup-shaped. Auxocytes: Spermatogonia with Round Nucleus, Heterotypic Mitosis, and Twelve Chromosomes (Figs. 10-62). Fic. 10. Auxocyte in the imperfect resting stage. Three darkly stained chro- moplasts with endochromatic granules. Leaders are centering towards the chromoplasts and connected with them. The spheres are reconstituted. The granosphere is cup-shaped ; the plasmosphere is indistinct and hardly to be defined from the cytoplasm. An archosome with two centrioles at the outer edge of the granosphere ; several accessory archosomes in the plasmosphere, all being con- nected by a thread and by rings of somosphere. The darker granules in the nucleus are chromomeres, containing each from one to three chromioles. Only a small part of the nuclear contents is sketched. Fic. 11. Auxocyte in the imperfect resting stage more advanced than the last figure. Two chromoplasts. The spheres are reconstituted, the inner one stained red being the granosphere. In its center is an archosome with two centrioles. Numerous accessory archosomes in the cytoplasm, some of them connected by threads of somosphere. The detail figure alongside shows the chro- matin network, each chromomere consisting of several chromioles. The leaders are projecting from the chromoplasts. 102 EISEN. (Vou. XVII. Fic. 12. Auxocyte in the beginning of the bouquet stage, the bouquet with twisted spireme segments. The segments are considerably longer than the nucleus and much twisted. They are all with one end attached to the chromo- plast. Two linoplasts stained red. The linin network is also stained red. The granosphere is cup-shaped ; at its upper margin is an archosome with two cen- trioles. Several accessory archosomes in the plasmosphere. Fic. 13. Auxocyte in the perfect bouquet stage. The twelve segments have shortened and straightened out; some are connected, two and two, by a chromo- plast, others are isolated. There are two dissolving linoplasts, intimately con- nected with the linin network. The spheres not yet fully reconstituted, but in a state of activity. A cell bridge connects two adjoining cells at the point of reconstitution. An archosome in the granosphere and accessory archosomes both in the spheres and in the cytoplasm. Fic. 14. Auxocyte in the perfect bouquet stage, but a little further advanced than the last. The segments are more contracted, and some are seen to be attached to chromoplasts, recognizable by their endochromatic granules. One linoplast stained red. The spheres are being reconstituted. A centrally situ- ated archosome with two centrioles. The granosphere is concave, with the con- cave side upwards, facing the reader. The radiations are from the cytoplasm and plasmosphere combined, the latter being in an active state of reconstitution. The letters a—d indicate detail figures drawn to a larger scale in order to be more distinct, but with the same objective and ocular. Figs. 14 @ and 14 4 are froma deeper focus or plane. Fic. 14 a. An accessory archosome with a somosphere with centrioles, the same one as figured in 14 é. Fic. 14 6. The granosphere focussed deeper than in Fig.14. The centrosomes connected by a thread of somosphere. Fic. 14 c. Detail figure of linin network showing the linin granules and the connection of the network with a linoplast. Fic. 14 d. Detail of three chromomeres showing the interior chromioles. Drawn on a somewhat larger scale than Fig. 14. Fic. 15. Auxocyte in bouquet stage with split spireme segments. Chromo- meres about twelve in each segment ; most of them are split, but not yet divided. About six chromioles in each chromomere. The outer sphere not yet fully recon- stituted, the granosphere being small, with a centrally located archosome with two centrioles. An accessory archosome in the plasmosphere. A red-stained linoplast in the nucleus. Several split chromoplasts connected with the spireme segments. Fic. 16. Auxocyte in the separated and crossed spireme stage. The divided and partly separated segments are not any more parallel, but cross each other in various directions. Some are attached to chromoplasts. Four linoplasts. The plasmosphere contains numerous rounded alveoles, containing secretions around which are seen the individual granules of the plasma. The granosphere is large and deeply stained. A centrally located archosome with two centrioles. Three accessory archosomes in the plasmosphere, each with several centrioles sur- rounded by somosphere. The granosphere is cup-shaped, with the concave part turned upwards. Fic. 17. Auxocyte, separated spireme stage. Four chromoplasts with endo- chromatic granules. Four linoplasts. The segments are twisted and separated No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 103 from each other, and all have been greatly lengthened out. The outer or plasmo- sphere is in a state of evolution, showing starlike radiations emanating from the vicinity of the granosphere. Many metaplasmic secreted granules in the plas- mosphere. The granosphere is angular in outline, cup-shaped, with a denser marginal wall consisting of closely packed granules of the plasma of the sphere. A centrally located archosome with two separated centrioles. Two accessory archosomes at the edge of the granosphere. Numerous paraplasmic granules of unknown nature in the cytoplasm, stained darker and connected by rings. Faint trace of a cell bridge emanating from the granosphere or from its immediate vicinity. Fics. 18-22. Auxocytes, all in the twisted and separated spireme stage. The dark nodes are the chromoplasts, from which start the separated spireme seg- ments. The two segments which twist around each other are the two halves of one original spireme segment. The segment having split, the two halves have separated, and becoming considerably elongated have twisted around each other in various ways. In Fig. 21 we see one dividing chromoplast which supported originally four undivided spireme segments, which latter have separated and twisted around each other and also have become much elongated. The small dark bodies are the chromomeres, containing each several chromioles imbedded in a chromoplasm and surrounded by an irregular network of linin, here and there stained gray by the iron-haematoxylin. It will be observed that in no instance are the distal ends (those not connected with the chromoplasts) of the spireme segments grown together, but simply cross each other. These segments will soon have contracted, after which,we will find them as represented in Figs. 23 and 24. Figs. 23 and 24. Auxocytes. Separated spireme segments which have yet more contracted. In Fig. 23 the segments are twisted around each other. The darkly stained nodes are the chromoplasts which hold the segments together. In Fig. 24 we have a more advanced stage, such as is found in the beginning of the angular spireme (Fig. 34). Only about one-half of the chromosomes have been represented in Fig. 24, the other half having been cut away by the knife. It will be observed that there are six original segments attached to the chromoplast, and that each one of them has become divided and contracted. Each such pair marked a, 4, c, d, é, f, etc., will form a bretzel-shaped chromosome, similar to those represented in Fig. 25, a, 4, c,d, e, f,etc. The linin network has not yet separated from the segments. Fic. 25. Auxocytes. A series of perfectly developed chromosomes from the metaphase and the anaphase. The figures are copies of selected chromosomes and intended to represent the most common forms assumed by them. Ata place marked “0” is seen the chromoplast adhering to the chromosome, while the free ends are marked “x.” In many instances it is difficult, and in others it is impos- sible, to determine which is the free and which is the chromoplastic end, as, for instance, in “7.” As a rule, the separation begins at the chromoplastic node “0.” At “yr” is seen a separated chromosome from the anaphase, the other half having been pulled to the opposite pole. The darker globules in the chromo- somes are the chromioles, of which there are thirty-six in each chromosome. In some of the chromosomes are seen traces of chromomeres. Fic. 26, a, 6, c, d, four chromoplasts with parts of leaders, from resting stages of polymorphous spermatogonia and auxocytes. In their interior are seen endo- 104 EISEN. , [Vou. XVII. chromatic granules. The linin is stained red, the chromioles are blue, but the chromoplasm is not differentiated. Congo-thionin-ruthenium red. Fic. 26%. Part of the linin network, from an auxocyte in the bretzel stage. The linin network is disarranged and has separated from the chromosomes. The small brown granules are the linin granula; the darker granules, of which there are comparatively few, are paralinin granules of unknown nature. The granules are connected by threads of the same apparent nature as the granules, and which may be considered as projections from the granules. Fic. 27. Auxocyte, in the bouquet stage; detail of the plasmosphere with two large accessory archosomes, each of which consists of a slightly amoeboid centro- sphere, a somosphere, and several interior centrioles of unequal size. The acces- sory archosomes are connected by a thin ring of somosphere, on which are also suspended granules of either archosomic or paraplastic nature. Fic. 28. Auxocyte in the irregular bretzel stage. Detail of the cytoplasmic end of the cell, showing the two spheres with accessory archosomes. The inner part of the granosphere has been drawn out by an archosome, the outer concave shell of the sphere being viewed sideways. Fic. 29. Auxocyte in the perfect bouquet stage. Detail showing the two spheres and part of the surrounding cytoplasm. The granosphere is cup-shaped, and differentiated into two parts, the outer one of which is in the form of a deeper stained ring, at the edge of which is seen an archosome with a faintly differen- tiated centrosphere. The somosphere and centrioles are not differentiated from each other ; the plasmosphere is well defined from the cytoplasm proper. The alveoles of the granosphere are seen to be surrounded by the individual granules of the spheres. Fic. 30. Auxocyte in the perfect bouquet stage. Detail of the spheres and of the free ends of some of the spireme segments, the chromomeres not yet being split. The chromomeres and the chromioles are slightly exaggerated as regards size, but other details are in exact proportion. The granosphere and the plasmo- sphere are both plainly alveolated, each alveole being surrounded by a single row of granules. An archosome with two centrioles in the granosphere. Three accessory archosomes in the plasmosphere. Three rows of alveoles in the plasmosphere. Fic. 31. Auxocyte in the bouquet stage. Detail of the two spheres. The granosphere is cup-shaped, consisting of one row of alveoles. The plasmosphere is less regular, with one or two rows of alveoles. At least five accessory archo- somes connected by rings of somosphere. On these rings are also suspended among the centrosomes paraplastic granules of undetermined nature. Fic. 32. Auxocytes in the bouquet stage. Detail figures of three adjoining cells. Two spindle bridges connect the three cells in the vicinity of the spheres. The spheres are not fully reconstituted, showing the chromosomic evolution to be more advanced than the radiosomic one. The accessory archosomes are connected by rings. The dark red spheres are the granospheres. The archo- somes are seen at the points where the spindle bridges join the spheres. Some of the accessory archosomes have the same structure as the archosomes. Fic. 33. Auxocyte in the bouquet stage; detail of the sphere not yet fully re- constituted. The archosome is connected with an accessory archosome by a fine somospheric filament very sharply defined; four centrioles in the upper somo- sphere and at least two in the lower one. The latter centrosome is probably the No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. 105 offshoot of the upper one. Alveoles are being formed in the plasmosphere probably by secretion of interalveolar and metaplasmic matter. Fic. 34. Auxocyte in the angular spireme stage. The separated segments have first contracted and then straightened out, having been angularly bent at the nodes, and the chromomeres have so approached that they are hardly to be distinguished from each other. Several chromoplasts are seen attached to the segments at the nodes, where they are joined together. Some chromioles are distinct in the segments. The granosphere is strongly stained and is seen to consist of one row of alveoles and several central ones. The plasmosphere and part of the cytoplasm are alveolate with distinct granules. A large archosome in the granosphere and an accessory archosome in the plasmosphere. There are no linoplasts left in the cell. Fic. 35. Auxocyte in bretzel stage, the chromosomes having the form of bretzels and rings. Only a few of the chromosomes are figured. The cytoplasm is alveolate with distinct granules. The granosphere is cone-shaped, with the denser part cup-shaped as usual. Near the apex of the cone lies the archosome with at least two centrioles. An accessory archosome at the upper left end of the granosphere. Fic. 36. Auxocyte in bretzel stage. Only a few of the chromosomes have been figured; one of them has been cut by the knife. The linin has separated from the chromosomes, and scattered to the opposite part of the nucleus. The cup-shaped granosphere is turned sideways, and appears as a crescent with one row of alveoles. The cone-like structure belongs probably exclusively to the granosphere. At its apex lies the archosome with two centrioles. Four separate accessory archosomes in the plasmosphere, the latter being strongly alveolated. Fic. 37. Auxocyte in bretzel stage. Only a few of the chromosomes are in the field. Several of them are connected in pairs with chromoplasts. One of the ring-like chromosomes is free. Several chromosomes show distinct chromi- oles. The linin network is scattered and not any more connected with the chromosomes. The plasmosphere is in dissolution; the granosphere is elongated. At the apex of the latter is situated the archosome, which appears to have been divided preparatory to the radiosomic process. The somospheres connected by a thin ring; there are three accessory archosomes. Fic. 38. Auxocyte in bretzel stage. The section is cut so that only the cyto- plasmic pole is seen. The archosome has left the granosphere and become divided. A small spindle is formed between the somospheres. The centrosphere is elongated ; from its outer margin radiate numerous mantle fibers. The plas- mosphere is greatly shattered, and the granosphere is only partly connected with the mantle fibers. There are numerous accessory archosomes both in the cyto- plasm and in the spheres. At the upper right-hand corner are seen the remains of a spindle bridge. Fic. 3814. Auxocyte in bretzel stage. Most of the chromosomes are halved by the knife. The linin network is scattered and retracted from the chromo- somes. The nuclear membrane is yet intact. The archosome is entirely divided and a small central spindle has formed outside of the granosphere. The latter is being used up as material by the fibers. The centrosphere is stained, and the various fibers are seen to emanate from its outer margin. The plasmosphere is scattered, and parts of it are seen in the cytoplasm. Three groups of accessory archosomes, some with three and four centrioles. 106 EISEN. [Vou. XVII. Fic. 39. Auxocyte in bretzel stage. The nuclear membrane is mostly dis- solved. The spindle is viewed from one of its poles, showing the mantle fibers to emanate from the outer margin of the centrosphere. The granosphere is partly used up, and the plasmosphere is mostly scattered in the cytoplasm. There are numerous accessory archosomes, some of which are connected by filaments of somosphere. A row of accessory archosomes is seen around the granosphere, all connected by a filament of somosphere. Many of the chromosomes show darkly stained chromioles. Outside of the plasmosphere the cytoplasm is fibrous, the fibers consisting of closely packed granules. Fic. 40. Auxocyte in bretzel stage. The chromosomes are rather heavy and contracted. The spindle is seen from one of the poles, and is in the figure not clearly definable. The granosphere is being used up by the spindle fibers. Much of the plasmosphere is being scattered ; some of it is seen far down to the right outside of the nucleus. The darker stained granules in the cytoplasm are the remains of the metaplasmic secretions of the plasmosphere. There are several accessory archosomes stained more or less deeply, some of them connected by a thread of somosphere. The linin network is scattered. Fic. 41. Auxocyte in bretzel stage. Several of the chromosomes are halved by the knife. The central spindle is well advanced. A set of contractile fibers has formed from both archosomes, but has not yet reached the chromosomes. A large accessory archosome at the upper end of the central spindle below the granosphere is situated in a much deeper plane than the archosome and is not in a direct line between the archosome and the granosphere. The plasmosphere is scattered in the cytoplasm. The part of the nuclear membrane nearest the man- tle fibers is dissolved. / Fic. 42. Auxocyte in bretzel stage. This figure, together with the previous one and several following, is arranged according to the development of the central spindle. The chromosomes in all these figures are in about the same stage of development. In the present figure the spindle is upright ; its axis con- nects with the axis of the cell. The granosphere has hardly begun to dissolve, its concave side is upwards. In the upper archosome are two centrioles, in the lower one is only one centriole. The contractile fibers are not deeply stained and are thus less well definable. Eight accessory archosomes, each with a centro- sphere and with from one to three centrioles. The plasmosphere is scattered, the remains are seen in two isolated groups at the left margin of the nucleus. The nuclear wall nearest the spindle is dissolving. Fic. 43. Auxocyte in bretzel stage. This is an abnormal cell as regards the position of the granosphere and the central spindle, the granosphere being gen- erally so situated as to be equidistant from both the poles of the spindle. At the upper margin are seen remains of the plasmosphere. An accessory archosome at the periphery of the granosphere. The contractile fibers are well differentiated, especially around the left pole of the central spindle. The nuclear membrane is dissolved nearest the central spindle. Fic. 44. Auxocyte in bretzel stage. The nuclear membrane is less dissolved than in the last figure. The granosphere is being used up. The contractile fibers are well differentiated and deeply stained ; none of them has as yet reached the chromo- somes. An accessory centrosome at the edge of the granosphere. The mantle fibers possess several denser nodes. The linin network has entirely separated from the chromosomes. The contractile fibers show a strongly granulated cytoplasm. PL. IV. Vol. XV. Journal. of Morphology. na Ss) 39. Spermatogenesis of Batrachoseps Noses] SPERMATOGENESIS OF BATRACHOSEPS. 107 Fic. 45. Auxocyte in bretzel stage. Only a few fragments of chromosomes are seen in the section. The central spindle is upright, its position depending on the position of the granosphere. At the upper pole are seen two archosomes, at the lower pole only one. The contractile fibers are strongly granular. A few small groups of accessory archosomes are seen to the left, the individual archo- somes being connected by threads of somosphere. Many of the individual granules of the granosphere are seen to be in direct connection with the mantle fibers. At the lower right-hand margin of the cell are seen parts of the scattered plasmosphere. Fic. 46. Auxocyte in bretzel stage. The granosphere is very much used up and in direct connection with the spindle fibers. The chromosomes are thrown in a bundle, all, however, being perfectly formed bretzels. At the poles of the spindle are seen several accessory archosomes surrounding the archosome. What I take to be the beginning of contractile fibers are seen to start out from the accessory archosomes. The linin network has left the chromosomes, and is broken up into globules, each one of which consists of several granules. At the lower margin of the cell are seen parts of the plasmosphere. Fic. 47. Auxocyte in bretzel stage, a transition stage between the last and the following figure in the metaphase. The last of the prophases. The central spindle is almost perfect. The remains of the two spheres are seen at the left in the cell. The contractile fibers are well advanced and several of them have reached the chromosomes. The latter are in the form of bretzels and rings. Numerous accessory archosomes as well as paraplasmic granules, difficult to dis- tinguish from each other. The nuclear membrane is entirely dissolved and the linin granula are scattered through the cytoplasm. The alveoli of the cytoplasm are very large and have assumed the forms of large vacuoles. Fic. 48. Auxocyte in a stage immediately preceding the metaphase. The chromosomes have not yet been drawn into the equator of the central spindle. One chromosome which is in its proper position has begun to divide. Two superfluous or unused linoplasts are seen in the cytoplasm. An archosome and numerous accessory archosomes are seen at each pole of the central spindle. Four groups of plasmosphere are scattered. The contractile fibers are distinctly beaded. In some of the chromomeres the chromioles are distinct; there are about six chromioles in a chromomere. Fic. 49. Auxocyte in a stage immediately preceding the metaphase. An archosome with several accessory archosomes at each pole. Some of the chro- mosomes are not yet in their proper position on the central spindle. There are five or more groups of scattered plasmosphere and secretions. Fic. 50. Auxocyte, metaphase. There are two archosomes at each pole, also numerous accessory archosomes. Three groups of scattered plasmosphere and its secretions. Several of the mantle fibers connect directly with metaplasmic granules of the plasmosphere. The group to the left has assumed its final posi- tion near the equator of the cell. Fic. 51. Auxocyte, metaphase. Only a few of the chromosomes are figured. One archosome at each pole, but several accessory archosomes. A number of linin granules as well as paraplasmic granules are seen in the cytoplasm. The contractile fibers are well defined, and one of them in the upper right-hand corner has been torn by the knife and has been bent outwards, a fact illustrating the independent nature of the contractile fiber. 108 EISEN. [VoL. XVII. Fic. 52. Auxocyte, metaphase. The section is cut at an angle with the cell axis and consequently the upper pole is seen slightly from above, while the lower pole is so viewed that the archosomes are not distinctly seen. The circle of dots around the upper pole are the starting points of the contractile fibers, which are seen to be connected with the somosphere and the centriole by a fine bar of dark- staining plasma. Several accessory archosomes in the cytoplasm. The red spots in the cytoplasm are the scattered remnants of the plasmosphere. The chromo- somes show here and there distinctly the chromioles and the chromomeres. This cell is unusually small for an auxocyte. Fic. 53. Auxocyte, metaphase. The chromosomes are regularly placed on the central spindle, all being in about the same stage of development. The spin- dle is halved and presents its inner concave surface to view. Chromioles are seen in all the chromosomes and chromomeres. Most of the chromosomes have commenced to separate. The red blotches are parts of the plasmosphere. The contractile fibers are all well defined, and some of them are seen to connect with the somosphere by a fine bar of darkly staining plasma. At the upper pole is seen one archosome, while at the lower pole there are two. The upper archo- some is connected with the contractile fibers in that part of the section which is not figured here. This archosome is darker and refractive, the two centrosomes being of a dull color and not refractive. The cytoplasm contains no accessory archosomes, but numerous dark-staining granules, which perhaps may be inter- preted as linin granules. Many granules are connected by rings or threads. See also Fig. 51. Fic. 54. Auxocyte, metaphase. Most of the chromosomes have separated, and some have begun to contract. The contractile fibers have also contracted ; they are strongly beaded. Chromioles are seen in the chromomeres. The archo- somes are large and distinct. A few accessory archosomes in the cytoplasm. In the central spindle is seen a separated chromatin granule. This figure is a com- posite one as regards the poles. A few chromosomes found in the following sec- tion were added to the lower pole. The accessory archosomes were also added from that section. Fic. 55. Auxocyte, anaphase. A stage succeeding that shown in Fig. 54. The chromosomes are drawn much nearer the poles. Chromioles are seen plainly in many places. An archosome at each pole. The contractile fibers are disappear- ing. The plasmosphere is accumulated at the left side of the equator. The central spindle is beginning to dissolve, and shows irregular vacuoles along a line where the coming new cell wall is to appear. A chromatin fragment in the cen- tral spindle. Numerous paraplasmic and linin granules in the equator of the central spindle. Fic. 56. Auxocyte, anaphase. The chromosomes are further advanced, approaching the confluent umbrella stage. On account of improper washing out, this figure does not show the details as well as the preceding and following figures. The cell is lengthening out and the central-spindle poles have been pulled down through the chromosomes. A few chromosomes are not yet sepa- rated from each other, but connected by chromoplasm. Fic. 57. Auxocyte, anaphase. The chromosomes are entering the confluent umbrella stage. The individual chromomeres are yet distinguishable, but the en- dochromatic granules of the chromoplasts have already come into plain view. The archosomes have diminished in size, now appearing as very faint points. PLY. Vol. XV Journal of Morphology. * Me pee Sather Spermatogenesis of Batrachoseps. PLVI. thology Vol. XVI. Journal of Mory Spermatogenesis of Batracho: e ps Nori] SPERMATOGENESIS OF BATRACHOSEPS. 109 The plasmospheric granules are seen near the equator of thespindle. The future cell wall is outlined, and several mantle fibers are seen connected with the plas- mospheric granules in the vicinity of the contraction in the equator. Fic. 58. Auxocyte, anaphase. The chromosomes in the umbrella stage. The chromosomes have lost their individuality, and only here and there does a pro- jecting point indicate theirformer outline. The distribution of the endochromatic granules of the chromoplasts indicates that the confluence is perfect. At the upper pole is seen the apex of the central spindle, with the remains of the con- tractile fibers under the form of four granules, corresponding to as many acces- sory archosomes. The archosome is seen at the very apex of the central spindle. The red blotches are part of the scattered plasmosphere. The alveoli of the cen- tral spindle are widened along the equator and along a line where the new cell wall is to appear. - Fic. 59. Auxocyte, metaphase. The confluent umbrella stage in which the con- fluence is perfect. Inthe umbrella are seen vacuoles and endochromatic granules. A cytoplasmic or false nuclear membrane is formed around the nucleus. Numer- ous polar fibers and mantle fibers connect the cytoplasmic membrane with the cell wall. The plasmosphere, now fragmented, appears as four agglomerations along the new cell wall separating the spermatocytes. The spermatocytes are more sep- arated than in Fig. 61, but this separation is only apparent as the cell in Fig. 61 is seen from the side, while the present one is viewed from the front. The spindle is much contracted in the middle, and the muscular nature of some of the fibers is indicated by the beading. A few accessory archosomes are seen below each nucleus. The poles of the central spindle are not visible. Fic. 60. Auxocyte, anaphase, ring-like, confluent umbrella. The two new spermatocytes are almost separated. The cytoplasmic membrane around the nucleus is being pulled away from the umbrella, and numerous fibers are seen to connect with the membrane. Numerous fibers from the poles of the spindle connect with the cell wall, separating the two spermatocytes. Several accessory archosomes are seen on the cytoplasmic membrane. Fic. 61. Auxocyte, metaphase, and confluent umbrella stage. The central spindle has contracted in the middle, and has been pulled through the um- brella. A large vacuole has appeared around each nucleus, the cytoplasmic membrane around the nucleus is being pulled away allowing the nucleus to expand. On the membrane are several accessory archosomes, from which start out fibers singly and in bundles. The fragments of the plasmosphere are in the equator at points where the new cell wall is being formed. The granules of this sphere are seen to be connected with fibers both from the poles and from the cytoplasmic membrane. This and several of the following figures are from differ- ent slides from the previous ones, the tissue having been stained much more intensely by the congo. The fibers of the central spindle are all strongly granu- lar and beaded like muscle fibers. The contraction from the old cell and the formation of the new cell wall is seen to proceed from one side only, which process appears to be normal. Spermatocytes or Spermatogonia of the Second Maturation Stage. Fic. 62. Spermatocytes. Two cells not yet entirely separated. The chromo- somes in the beginning of the chrysanthemum stage, emerging from the confluent IIO EISEN. [VoL. XVII. stage. Darkly stained bars indicate the new chromosomes in the confiuent mass, all pointing in the direction of the cell axis. The spindle shows several con- tractile fibers ending on the cytoplasmic membrane which has receded from the chromosomes. On this membrane are seen several accessory archosomes, from some of which radiate fibers. From one of these archosomes proceed the remains of retractile fiber cones. The reddish blotches are the remains of the plasmosphere. Some of the accessory archosomes are furnished with distinct centrospheres. In the chromosomes are seen a few endochromatic granules, characteristic of the chromoplasts. The cell wall is made up of cytoplasmic granules. Fic. 63. Spermatocyte, in the chrysanthemum stage, having entered the pro- phase in which the individual chromosomes are being reconstituted. Only a small section of the nucleus is seen. Only one cell is figured. The cytoplasmic or false membrane has been pulled back in order to allow the growth of the nucleus. The central spindle is fully retracted and the archosome has assumed its position at the apex of the fibers. Several accessory archosomes pulling fiber cones towards the cell wall. Numerous accessory archosomes attached to cone fibers, others are seen on the cytoplasmic membrane. Many of the accessory archosomes are seen to have a centrosphere. Fic. 64. Spermatocyte. Spindle bridge ; remains of the central spindle which has greatly contracted, many of its fibers showing muscular beading. One of the dark granules is probably the archosome, it being situated where the granosphere is being reconstituted. The cells which were connected by this bridge were in about the same stage as the cell figured at 63. Fic. 65. Spermatocyte in the chrysanthemum stage, more advanced than Figs. 63 and 64. The chromomeres and chromosomes are plainly indicated and partly individualized. The section passed obliquely to the central spindle, showing the cytoplasmic or false nuclear membrane with three or more accessory archo- somes, from which radiate several fiber cones. This is not a free cell, but one which was connected with another cell by a spindle bridge. Fic. 66. Spermatocyte in the chrysanthemum stage. The cells are not yet separated, but connected by a cell wall and a spindle bridge. Several fiber cones are formed on the cytoplasmic membrane, pulling the latter away from the nucleus. The accessory archosomes are not as distinctly stained as in the other cells, which is due to the greater washing out of the iron stain. A mid-body in the center of the spindle bridge. The retractile fibers are emanating from the apex of the upper spindle pole. Fic. 67. Spermatocyte in the chrysanthemum stage; the cells are not yet sepa- rated. The central spindle is greatly contracted, the fibers at each pole are being retracted and condensed into a reconstituting granosphere. The fiber cones have advanced towards the cell wall, the accessory archosomes actually resting on the cell wall. Several paracellular bodies are seen on the cell wall, some being con- nected with the cell by fine threads. Retractile fibers emanating from the poles of the central spindle. The accessory archosomes at the poles of the fiber cones are too much washed out to be distinct. From two to three fragments of the plasmosphere in each cell, easily identified by their deeper stain. Fic. 68. Spermatocytes in the chrysanthemum stage. The two cells are more separated than in the preceding figures. The fiber cones have reached the cell wall, and some of them have receded from the cytoplasmic membrane, The Journal of Morphology Vol. XVI. j PLVIL 59. Lith. Werner & Winter Frankto Spermatogenesis of Batrachoseps. No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. III granospheres are being reconstituted at the poles of the central spindle. In the upper cell are seen three fragments of plasmosphere near the cell wall. The pole of the upper central spindle rests on the cytoplasmic membrane, while the pole of the other cell ends in the cytoplasm. A linin network is forming between the chromosomes in the lower nucleus. Archosomes and accessory archosomes are too much washed out to be distinctly visible. The mid-body consists of a double row of granules. Fic. 69. Spermatocyte in the chrysanthemum stage. The linin network is appearing among the chromosomes. The fiber cones are pushing out the cell walls in both cells. The accessory archosomes at the poles of the cones are well defined; some are also seen on the cone fibers. The fragments of the plasmo- sphere are seen in both cells, stained dark red. There are two archosomes at the pole of the central spindle of the lower cell. At a deeper level the false nuclear membrane was distinctly seen in each cell. Fic. 70. Spermatocytes emerging from the chrysanthemum stage and entering the second prophase. The two cells are only connected by a spindle bridge. The chromosomes are separated, though some are yet connected by chromoplasts, which latter are now located at the angle where the two prongs of the chromo- some meet. The cytoplasmic membrane is yet seen around the nucleus, the latter having filled out the vacuole. But a true nuclear membrane or karyotheca has also been formed directly around the chromosomes, showing that the two mem- branes are of different origin. Accessory archosomes are seen on the cytoplasmic or false nuclear membrane; some are also seen on the cone fibers. Two fragments of plasmosphere in the lower cell along the new cell wall. The granosphere is being reconstituted, especially around the pole of the central spindle in the upper cell. The chromosomes in the lower cell are further advanced than those in the upper cell. Fic. 71. Spermatocyte in the checkerboard stage, the chromomeres being much separated. The fiber cones are yet pushing out the cell wall, though some of them have evidently begun to dissolve. The new nuclear membrane has formed around each nucleus. A large plasmosphere in each cell. Accessory archosomes at the pole of each fiber cone. A mid-body on the spindle bridge. Fic. 72. Spermatocytes connected by a spindle bridge on which is seen a mid- body. The fiber cones are disappearing. The two spheres are reconstituting separately, later on to be united. Many accessory archosomes on the fibers as well as in the cytoplasm. Fic. 73. Spermatocytes in the checkerboard stage, though further advanced than the last figured cell. The fiber cones, however, are less degenerated, and the granosphere is less advanced. A comparison of the two figures, 72 and 73, shows that here, as elsewhere, the chromosomic process and the radiosomic process do not run quite parallel, but that one may be in advance of the other. Thus in 73 the nucleus is further advanced than the nucleus of 72, but the cytosome of 72 is further advanced than the one of 73. Fic. 74. Spermatocyte, free and in the checkerboard stage. The fiber cones are yet faintly traceable. Several rings of somosphere with accessory archo- somes. An unusually small cell. Fics. 75 and 76. Spermatocytes, free, in the checkerboard stage. These two figures represent two sections of the same cell. The numerous fiber cones have not yet begun to recede. Several rings of somosphere with accessory archosomes. 112 EISEN. [Vou. XVII. The chromomeres are seen to be of different sizes and to contain a variable num- ber of from nine to three chromioles each. Fic. 77. Spermatocyte, free and with chromosomes in the checkerboard stage. The chromomeres are well separated and contain about three to nine chromioles each. The spheres are being reconstituted together, the inner one being the granosphere and the outer one the plasmosphere. An archosome with two centrioles on the plasmosphere. The fiber cones have not yet disintegrated, the upper one with a distinct accessory archosome at the apex. Fic. 78. Spermatocyte, free and with the chromosomes in the chrysanthemum stage. The chromomeres are much separated, though the staple-shaped form of one of the chromosomes is distinct. The spheres are reconstituting in the upper left corner of the cell. Accessory archosomes connected by a ring of somo- sphere. The remains of the fiber cones are recognizable in the four projecting corners of the cell. A linin network is stained reddish. Fic. 79. Spermatocyte, free, the chromosomes in the beginning of the con- traction stage or the third prophase. All traces of fiber cones have disappeared. The spheres are being reconstituted, the darkly stained one being the granosphere. Numerous accessory archosomes in the plasmosphere. Fic. 80. Spermatocyte, free and the chromosomes in the beginning of the con- traction stage. The two spheres are being reconstituted. Numerous accessory archosomes on the plasmosphere. Figs. 80-82 are in very much the same stage of development, but representing a serial development and contraction of the chromosomes. In Figs. 81 and 82 the plasmosphere is reconstituted in the opposite end of the cell from the granosphere. This is frequently the case in the spermatocyte, and saves the redistribution of the sphere to the equatorial of the new spindle. Fics. 81 and 82. See Fig. 80. Fic. 83. Spermatocyte. Contraction stage in which the chromosomes are again assuming their staple form, and in which the linin network is separating from the chromosomes. This stage corresponds to the bretzel stage of the auxo- cytes. Figs. 83 and 84 are in nearly the same stage. The plasmosphere is recon- stituted in the opposite part of the cell from the granosphere. Numerous acces- sory archosomes around the granosphere. The similarity of all is so great that it cannot be decided which of them is the archosome. Chromomeres show the interior chromioles. Fic. 84. See Fig. 83. Fic. 85. Spermatocyte in the beginning of the angular chromosomes, the fourth prophase. The chromosomes have become narrower and the margins are more even. This stage corresponds to the angular segments of the auxocytes, though there are some important differences. The chromoplasts, for instance, are very prominent in the auxocyte, while in the spermatocyte they are only now and then to be distinguished from the chromosomes. Only a few of the chromosomes are figured. At the lower margin of the cell are seen the spheres, but it is doubt- ful if the round mass is anything but the plasmosphere. The linin network is disintegrated and retracted from the chromosomes. Several of the superfluous archosomes have been expelled from the cell and are now seen attached to the exterior of the cell wall. They have also swelled up and increased perhaps five- fold in size, but to what extent their inner structure has become modified by the swelling up is not clear. It seems, however, most probable that the somosphere PL.VII.. Vol. Xvi Journal of Morphology. —- 65. Spermatogenesis of Batrachoseps. PLIX. Journal of Morphology. ae ol.XI UW. 735. 79. 78. ¢ Fe Spermatogenesis of Batrachoseps re | No. I.] SPERMATOGENESIS OF BATRACHOSEPS. I13 has filled out the centrosphere, and that the centrioles have separated from each other. Fic. 86. Spermatocyte in the angular chromosome stage. This and the previ- ous figure are very much in the same stage as regards the nucleus. The spheres are not distinct and there are no expelled archosomes. Three accessory archo- somes at the upper part of the cell. Fic. 87. Spermatocyte in the beginning of the knotted chromosome stage. The chromosomes are separated and, have not yet accumulated in the center of the cell. Numerous accessory archosomes, each one surrounded by an amoeboid centrosphere. A very small granosphere. Chromioles are seen in the chromo- somes. Fic. 88. Spermatocyte in the knotted chromosome stage. A distinct grano- sphere, a scattered plasmosphere, and numerous accessory archosomes in the cytoplasm. Some of the archosomes are being expelled from the cell. Chromi- oles are seen in the chromosomes. Fic. 89. Spermatocyte in the knotted chromosome stage. Several fiber cones are yet seen, and it is probable that two of them will form the central spin- dle. Numerous accessory archosomes on the fibers of the cones, some of the fibers evidently dissolving the nuclear wall. Fic. 90. Spermatocyte in the knotted chromosome stage. The nuclear mem- brane is completely dissolved by two fiber cones. The individual chromosomes are so tightly knotted that they are difficult to segregate one from the other. The chromosomes are only approximately correctly figured. These two fiber cones are probably the beginning of the central spindle. A sphere is seen in the upper apex of the cell; many accessory archosomes and an archosome with an amoeboid centrosphere. Fic. 91. Spermatocyte in the knotted chromosome stage. Only a few chro- mosomes are seen in the section. The nuclear membrane has been dissolved by the fiber cone emanating from the upper apex. The linin network is scattered and the granules are mixing with the cytoplasm. Accessory archosomes on the fibers and one at the lower pole of the cell. Each one is furnished with an amoe- boid centrosphere. Some of the chromioles in the chromosomes are distinct. Fic. 92. Spermatocyte in the V-stage; the chromosomes are in the center of the cell. Only one pole of the central spindle is developed, there being no trace of the other pole. The nuclear membrane is dissolved. A plasmosphere to the left of the future equator. A dividing archosome in the pole of the spindle. Fic. 93. Spermatocyte in the beginning of the V-stage, the chromosomes being in the center of the cell. A central spindle is being formed out of two old fiber cones. At the apex of each cone is an accessory archosome which is now assum- ing the function of an archosome. Fic. 94. Spermatocyte. Chromosomes in the knotted stage, but the central spindle has already formed out of two opposing fiber cones. This is the charac- teristic form of the spindle in this stage, the two poles being greatly depressed. An archosome at each pole. There is no distinction between the mantle fibers and the central spindle fibers. I found several cells like this one, but no interme- diate stages with Fig. 93. Fic. 95. Spermatocyte. In the V-stage, not yet in the metaphase. The upper pole with several accessory archosomes, one of which is the spindle archo- some. The lower pole has probably been cut off by the knife. II4 EISEN. [VoL. XVII. Fic. 96. Spermatocyte in the beginning of the V-stage. Half of the spindle has been cut off. There are three accessory archosomes at the upper pole, one of which probably has the function of a spindle archosome. The plasmosphere is scattered in the equator. The archosomes at the pole have a remarkable simi- larity to the expelled archosomes figured elsewhere (Fig. 85). Fic. 97. Spermatocyte in the beginning of the V-stage, or the end of the knotted chromosomes. The central spindle is finished, but the chromosomes are not yet in position. The plasmosphere is in the equator. The accessory archo- somes lie in a ring around the poles of the spindle. Fic. 98. Spermatocyte in the V-stage just before the beginning of the meta- phase. The chromosomes in the form of perfect V’s, which, however, are not yet distributed’ along the spindle. The mantle fibers are connected with the granules of the plasmosphere. An archosome at each pole, also a large accessory archosome with an amoeboid centrosphere. Contractile fibers are forming and projecting from the centrosphere of the archosomes. Fic. 99. Spermatocyte in the perfect V-metaphase. The contractile fibers are formed and connect with the chromosomes. An archosome at the upper pole; the lower pole is cut off. A trace of the plasmosphere to the left of the equator. Only a few of the chromosomes are figured. Fic. 100. Spermatocyte in the perfect V-metaphase. Only a few of the chro- mosomes are figured. The chromosomes are splitting at the bottom or angle of the V. An archosome at each pole surrounded by a pale centrosphere. The contractile fibers are plainly beaded. Blotches of plasmosphere stained pink. Many chromioles are seen in the chromosomes. Fic. 101. Spermatocyte in the perfect metaphase; some of the chromosomes are separating, while others are not yet in their proper position on the central spindle. Several larger groups of plasmospheres along the equator. An archo- some at each pole, surrounded by several accessory archosomes, each one with developed centrosphere. FIG. 102. Spermatocyte in the beginning of the anaphase. An archosome at each pole, and a few accessory archosomes in the cytoplasm. Chromomeres and chromioles visible in the chromosomes. Fic. 103. Spermatocyte in the perfect V-anaphase. The chromosomes have separated, the chromomeres have mostly disappeared, but the chromioles are yet distinct, and arranged in two parallel rows in each chromosome. The plasmo- sphere is scattered along the equator of the contracting spindle. The mantle fibers are seen to be connected with the plasmospheric granules. An archosome at each pole. Fic. 104. Spermatocyte in the beginning of the confluent stage of the ana- phase. The contractile fibers have shortened and the chromosomes have become partly confluent. The chromomeres have disappeared, but the chromioles can yet be distinguished here and there. Parts of the plasmosphere along the equator. Fic. 105. Spermatocyte in the beginning of the confluent stage of the ana- phase. The cell has already begun to divide and a new membrane is being secreted along the vacuolated equator by the plasmospheric granules. The polar cones of the central spindle have so shortened as to be hardly distinct. The archosomes are reduced in size and barely visible. A few of the chromioles are distinct in the chromosomes. Journal of Morphology. Vol.Xvil ; ane 81. 82. oe a Spermatogenesis of Batrachoseps. Journal of Morphology. Vol. XVII. 89. 90. ~ $2 SEagere : r° na gee os ae 7 De 1. 96. PURI, Spermatogenesis of Batrachoseps. PL XM. S . : g iS = 3 i = | = a a Ce & . wel | x ' *%e - a Sh : % fae, op ; 9 Ss 1 Pa m =3 SS N : ht S § Journal. of Morphology. E atrachoseps of oO itosenesis Sperm: No. 1.] SPERMATOGENESIS OF BATRACHOSEPS. I15 Fic. 106. Spermatocyte in the confluent stage, but the confluence is not yet perfect. The polar cones are mostly gone and the archosomes so faint as to be indistinct. The new cell membrane has formed along the equator of the central spindle. The latter has contracted, several of its fibers being beaded. Many plasmospheric granules along the new membrane, especially on the left side. Fic. 107. Spermatocyte in the perfectly confluent umbrella stage. The cells are almost separated and are only connected with each other by the central spindle. The spindle is greatly contracted, showing some beaded fibers. No dis- tinct archosomes, and the polar cones have so descended into the nucleus as to be no more visible. A false nuclear membrane is being formed around the nucleus. The pole of the lower spindle is just above the nucleus; at the apex is a small archosome. In the upper cell is a large accessory archosome. Fic. 108. Spermatocyte in the end of the confluent stage, the chromosomes just beginning to reappear in the chrysanthemum stage. The cytoplasmic mem- brane is fully formed around the nucleus, and is now being pulled away by the centrosomes. The granospheres are being reconstituted around the poles of the spindle. Parts of the plasmospheres are seen along the new cell walls. A mid- body on the central spindle, which latter has been greatly contracted. The poles of the central spindle are connected with the cytoplasmic membrane by a few fibers. Fic. 109. Spermatid. In a rather advanced stage of development, the nucleus having assumed its full size. The two spheres have been reconstituted. An archosome is seen to the left of the granosphere. The nucleus is in the checker- board stage. Several paracellular bodies are attached to the exterior of the cell. These are probably expelled particles of the spheres, which have become inflated. They show in their interior a fibrous structure. There are two distinct chromo- plasts in the nucleus, recognizable by their endochromatic granules. The remains of a spindle bridge at the upper pole of the cell. Fic. 110. Auxocyte. Detail figure of one of the central spindle poles, show- ing the formation of the contractile fibers and their connection with the somo- sphere of the archosome. In the center of the field is seen a large archosome consisting of a darkly stained inner centriole and somosphere, surrounding which is a large unstained centrosphere. Twelve fine bars connect the centriole with the contractile fibers which begin on the outer margin of the centrosphere. On the upper ends of the centrosphere only the ends of the contractile fibers are seen. Several accessory archosomes in a ring around the archosome. The red, granular plasma, divided in three groups, is the remains of the plasmosphere. Each accessory archosome possesses a centrosphere. The contractile fibers are strongly beaded. Fic. 111. Auxocyte. Detail figure of a pole of the central spindle, showing the archosome and its connection with the central spindle fibers and the con- tractile fibers. The archosome is large and contains two centrioles, each sur- rounded by a somosphere. Several accessory archosomes, one of which appears to be the starting point of a contractile fiber. The contractile fibers are strongly beaded. Zeiss Apo. 2 mm., Apert. 1, 40, Oc. 18. Fic. 112. Auxocyte. Detail figure of an archosome; the contractile fibers start from the outer margin of the centrosphere. The chromosomes are in the anaphase, with the contractile fibers greatly contracted. They are strongly beaded, the beads being situated between a covering of granulated fibers, evi- 116 EISEN. [Vo. XVII. dently forming a casing to the granules. The beading of the contractile fibers is probably of the same nature and origin as the mid-body. That is, the beads may serve as storage reserves of plasma to be used when the contractile fiber is lengthened or shortened. When suddenly lengthened on account of strain the plasma is probably supplied by the beads, and vice versa; when the contractile fiber requires to be suddenly shortened its superfluous plasma is quickly accumu- lated in the beads. Chromioles are plainly visible in the chromosomes, especially in the one to the left. Zeiss Apo. 2 mm., Apert. 1, 40, Oc. 18. Fic. 113. Auxocyte. Detail figure of an archosome and six of its contractile fibers, showing them to start from the outer edge of the centrosphere. Some of the fibers connect with the inner centriole by a fine bar of somosphere. The contractile fibers are strongly beaded, somewhat of the nature of a muscle fiber. The beads are situated in zigzag fashion and covered by a sheathing of fibrous nature. There are three strongly stained accessory archosomes at the pole. The chromosomes are only indicated. The figure is drawn to a larger scale. Fic. 114. Spermatocyte. Detail figure of a fiber cone showing the connection of the fibers with the accessory archosomes. Several of the latter possess amoe- boid centrospheres. The nucleus is in the checkerboard stage. Fic. 115. Spermatocyte. Detail figure of a fiber cone. The outer edge of the cone forms also the outer cell wall. An accessory archosome with several centrioles is near the apex of the cone. This cone is less advanced in dissolu- tion than the one figured in Fig. 114, though it is from the same cell. Fic. 116. Spermatocyte. Detail figure of a fiber cone in dissolution, showing the granulated and beaded structure of the fibers. At the apex is an accessory archosome. The outer edge of the cone is closely pressed against the cell wall. Fic. 117. Spermatocyte. Detail of a fiber cone in dissolution. The accessory archosomes have left the apex of the cone and are now congregating around the reconstituting granosphere. Each centrosome possesses an amoeboid centro- sphere. Some of the centrosomes are yet attached to the cone fibers. The outer lining is the cell wall. Fic. 118. Spermatocyte. A nucleus in the chrysanthemum stage, showing the staple-shaped chromosomes in a stage of growth. The nuclear membrane is formed in the immediate vicinity of the chromosomes. The chromomeres and some of the chromioles are distinct. The linin network is stained red. Fic. 119. Spermatocyte. A nucleus and two detail figures of chromosomes. The details are drawn on a slightly larger scale, but with the same magnification and objective. The chromosomes are further advanced than in Fig. 118. The chromomeres are separating. Some of them contain eight or ten, others only three to four chromioles. Fic. 120. The homoeotypic mitosis by equation division of the spermatocyte from the perfectly split / to the confluent umbrella stage. a@ to fshow the V- shaped chromosomes as they are thrown on the central spindle; some are seen in front view, others in side view. The fibers connecting with the chromosomes are contractile fibers. . to 4 show the chromosomes in the act of separation, being pulled apart by the contractile fibers. At 7 is seen one of the daughter-chromo- somes in which the chromioles are very distinct. z to £,chromosomes after the halves have separated and the daughter-chromosomes have formed. J/, m, chromosomes in the confluent umbrella stage; in 7 no endochromatic granules are seen on account of too dense staining. In m many endochromatic granules. PLXMI. Journal of Morphology Vol. Xvi. 108. 105. 11+. T11. i 110. 109. 115. Spermatogenesis of Batrachoseps ar No:\5.] SPERMATOGENESIS OF BATRACHOSEPS. PE All the above chromosomes are copies from actual chromosomes and not dia- grammatic. Fics. 121 and 122. The heterotypic mitosis by equation division. A diagram- matic representation of the development of leaders of an auxocyte into chromo- somes, their splitting and equation, in a progressive series from a to/. a, two leaders connected by a divided chromoplast, the latter marked c. Numerous chromomeres on the leaders, each with several chromioles. 6, the same two leaders, the chromomeres having contracted into a smaller number, each chromo- mere having more chromioles, which latter have now been arranged in two parallel rows in each chromomere. This is the beginning of the stage in which the leader splits. c, the same two leaders, but which have now split into four leaders, each one of which will become a single chromosome in the daughter- nucleus. The two halves of one leader form the bretzel-shaped chromosome. Observe that the chromomeres have again separated and become smaller. d, the same two leaders, the chromomeres having contracted anew, the whole leader having shortened. ¢, the same two leaders, which have yet more shortened, and the chromomeres have contracted into a smaller number; the two chromoplasts are seen at the junction of the two leaders. /, a single leader which has become separated through the division of the chromoplast. It now forms a perfect bretzel- shaped chromosome, consisting of two prongs connected by a dividing chromo- plast. The two prongs of the leader have crossed each other and thus formed the bretzel. g to & are various forms of bretzel chromosomes, some of which have their free ends overlapping, while two of them have the ends actually grown together. 7, a chromosome which has just undergone equation division. The parting has taken place through the chromoplast; cc, the two ends which were grown together, are yet united by two fine threads of chromoplasm. m, two chromosomes in the confluent umbrella stage, with several endochromatic granules. XIII. STAINS, FIXATIVES, OPTICAL APPARATUS, Etc. Congo, No. 1209, The Substantive Colors Co. Actien Gesellschaft fiir Anilin- Fabrication. Thionin, Cogit & Co., Paris. Rutheniumroth, Dr. G. Griibler & Co., 200, Leipzig. Iridium Chloride, Merck & Co., Darmstadt, Germany. Apochromat No. 412, 2 mm., Apert. 1. 40, Homog. Immers. Carl Zeiss, Jena. Apochromat No. 262, 3 mm., Apert. 1. 40, Homog. Immers. Carl Zeiss, Jena. All the chemicals and optical apparatus furnished by Charles C. Riedy, San Francisco, Cal. as VD y th 1 4St, 1 CAA NEES i if PLXIV; journal of Morphology. Vol.Xvit. W194 M7. { a ¥ By Daf Cae oe Spermatogenesis of Batrachoseps vv o PROFESSOR COLLETIT ON THE MORPHOLOGY. OF THE CRANIUM AND THE AURICULAR OPEN- INGS IN THE) NORTH-EUROPEAN SPECIES O8 SHE PAMIMICY (StTRIGID A: R. W. SHUFELDT, M.D. One of the most extensive and valuable contributions to the subject of the anatomy of owls, and their classification, was given to science by Prof. Robert Collett of the Zodlogical Museum of Christiania, Norway, in 1881. This brochure was read by him before the Scientific Society of that city on December 9, and published in its Proceedings for the same year. This memoir printed nearly forty pages octavo, and is illustrated by three folding lithographic plates, giving thirty- five figures of the skulls and ear-parts of various species of the family considered, the whole being entitled Cvanzets og Oreaabningernes Bygning hos de nordeuropeiske Arter af Familien Strigide. Appearing, as it did, in the Norwegian language, the usefulness of this very excellent piece of work was to a great extent limited, and many comparative anato- mists all over the world could not readily employ it or avail themselves of its results, both of which uses it so amply merited, for the very reason that it was in Norwegian, a language rarely mastered by naturalists at large. With the view of obviating all this, and bringing the investigations of Professor Collett in the osteology and taxonomy of the Strigz- de before the English-speaking world, I have long planned to have his memoir in these fields translated, but, from one cause or another, the task had to be postponed. Events of a partic- ularly unfortunate nature stood in my path during the entire summer of 1895 and late into the following autumn, but with the opening of the year 1896, circumstances became far more propitious for the resumption of all my work in comparative 1 ae) 120 SHUFELDT. [VoL. XVII. morphology, and among the first tasks undertaken by me was the translation of this worthy contribution to avian anatomy by my esteemed colleague in Christiania. This has been ren- dered possible through the kind assistance of my young Nor- wegian friend, Miss Alfhild Dagny Lowum, now my wife, who, with great patience, made the literal part of this translation. With this before me, Professor Collett’s memoir was given its English version in the language of science. My private osteological cabinets contain the skeletons of many species of owls, and the crania of these I have compared with his researches as the labor of translation progressed, giving such additional information as was thus obtained in footnotes, and signed by my own initials. JI have also seen fit to rearrange his figures, redrawing some of them for text-figures, and retain- ing those for lithography that especially demanded that kind of reproduction. The present contribution, then, consists in a full and com- plete English translation of Collett’s memoir, supplemented by footnotes of my own, and a reproduction of all the figures given in the original Norwegian work. And to this I have added some of the more recent opinions of recognized authori- ties upon the subject, relative to the systematic position of the Strigide, thus bringing the whole up to date and ren- dering the entire memoir available to students of comparative morphology everywhere; it being, as it were, a comprehensive treatise upon the value of certain structures to be found in the head and cranium in owls in the classification of that family, together with their relations to other groups of birds, as those relations are understood at the present time. Professor Collett says : «The ten North-European species of the family Strzgzde, all of which belong to the subfamily Lwbonine (the other sub- family, which is represented by Stvzx flammea, does not occur in Scandinavia), can be arrayed in six (6) groups based upon the morphology of the cranium and upon the structure of the external ear-openings and their dermal appendages.” It is clear from the following table that only the first of these groups, which includes Surnia funerea, Glaucidium passerinum, Kit LE CRANIUM TIN TRE, OWES. No: T.] Family, Bubonine. Order, Striges: A. Dermal F aGHGtlaT I. Cranium flaps symmet- absent. | rical. I. Cranium symmet- rical. B. Dermal auricular flaps present. II. Cranium asymmet- rical. I. sect. ‘Process . Group. Auric- dexclaped ee ular openings jueae [ symmetrical. 2. Sect. Jugal lin- Cale eae 2. Group. Auricular opening largest upon the right side ... . 3. Group. Auricular openings asymmet- rical; resembling a gill-slit; aural skin-flaps of equal size, as are also the auricular openings. 4. Group. Auricular openings asymmet- rical; reniform ; the skin-flap larg- est upon the right side. . . 5- Group. Cranium asymmetrical upon [ the right side; ear-openings reniform 4 in outline ; and the skin-flap largest upon the right side. a. Supraorbital processes Styliformi esos oe 6. Supraorbital processes broad and short. . . a. Frontals narrowly sculpt. 6. Frontals broadly sculpt. a. Os squamosum slightly asymmetrical. =. 6. Os squamosum markedly asymmetrical. . . . 6. Group. Bilateral asymmetry of the cranium; auricular openings wide; equal in size; dermal flap similar to cranial asymmetry . .. . a o> Io. Surnia funerea (Linn.) 1776. 1776. Wyctea scandiaca (Linn.) 1766. Bubo ignavus (Forst.) 1817. Asio accipitrinus (Pall.) 1771. Asio otus (Linn.) 1766. Syrnium aluco (Linn.) 1766. Syrnium uralense (Pall.) 1776. 1789. Wyctala tengmalmi (Gmel.) 1788. 122 SHUFELDT. [VoL. XVII. and Vyctea scandiaca (all lacking ear-flaps), have perfectly symmetrical auricular openings and crania. In all the other groups, including seven species, the auricular apertures are unequal in size or asymmetrical in other ways. On the two last groups, which include Syrntum uralense, Syrnium lappont- cum, and Nyctala tengmalmi, the asymmetry is so pronounced that even the cranium is more or less involved. This asymmetry of the auricular openings, their dermal flaps, or the cranium, commonly exhibits itself as an anoma- lism of the right side of the head, so the opposite or left side in these must be regarded as the normal one. This anomalous condition in the majority of our species, so far as the auricular openings and their dermal flaps are con- cerned, consists in these strictures being larger and of greater width on the right than on the left side. Where this condi- tion also exists in the cranium, it is again the right side which exhibits the anomalous development. It is only in Wyctala tengmalmi wherein we find that both sides present the con- dition referred to, and perhaps the most so upon the left side. In the two species of Aszo, where the irregularity is confined to the dermal parts of the aural apertures, the right side must again be regarded as the normal side. /¢ would appear that in- asmuch as the internal ear and the brain cavity are perfectly symmetrical, neither of these parts enter into this anomalous state of affairs. The six groups into which the North-European species fall can be briefly characterized as follows : Group I. Dermal ear-flaps absent. Cranium and auricular openings symmetrical. a. Jugal with an elevated osseous apophysis. I. SURNIA FUNEREA (Linn.). 2. GLAUCIDIUM PASSERINUM (Linn.). Auricular openings of medium size or small. Osseous crests on os Sguamosum conspicuously individualized; viewed anteriorly they come into plain sight at the posterior aspect of either orbit. Posterior periphery of either orbit sharp where formed by the frontal bone. The greatest NO: 'k.]] THE CRANIUM IN THE OWLS. 123 vertical height of the cranium is posterior to the orbits. Vomer rudimen- tary. Jnfraoccipital foramen present, and large in the case of G. pas- serinum. The supraorbital processes in S. fumerea long and styliform. Crania lack the superficial median furrow upon their superior aspects. 6. Jugal linear. 3. NycTea scanpiAca (Linn.). Auricular openings of medium size and placed inferiorly. Osseous crest of os sguamosum comparatively small, and xon-united superiorly ; viewing the skull from in front, they are almost entirely concealed by the orbits. Vomer rudimentary. Supraoccipital foramen present. Median furrow on superior aspect of cranium present. To this first group, then, which includes species without dermal ear-flaps, and where no asymmetry is present in any part of the head, belong Surnia funerea, Glaucidium passert- num, and Nyctea scandtaca. Of these three, the two first-named species constitute a subgroup of themselves, since in certain of their cranial char- acters which they exhibit in common and in which they differ from the Norwegian species, they must doubtless be con- sidered, systematically speaking, as allied to each other. Both Surnia funerea and Glaucidium passerinum develop, superiorly, upon the jugal bone an elevated, oblong process of some length, while this bone in all the remaining North-European species is linear. Further, the superior aspect of the skull is flat and entirely lacking in a median furrow, which latter in _all the other species is present. Within this group the crania can be distinguished in the two species one from the other, in addition to the difference in size, by the feebler development of the mandibles in Glauctdium passerinum, which in its case, as compared with the cranium proper, are shorter than are the mandibles in any other species. Further, the supraoccipital foramen in this species is unusually large, both relatively and absolutely ; in fact, larger than it is in any other form. In addition thereto, Surnia funerea has the supraorbital processes long and spiculiform, approaching in this respect the diurnal Raptores. Nyctea scandiaca, constituting the second subgroup, has 124 SHUFELDT, [Vou. XVII. another type of cranial structure. In it the orbits are notably large, and the mandibular part strong. The jugal bone is linear, and the supermedial furrow of the cranium is well marked. The auricular openings in most of their characters agree with those forms already described, in being relatively small or of medium size, and in lacking any external dermal conch, or ear-flap. Group II. Aural skin-flaps absent. Cranium symmetrical. Auricular apertures largest upon the right side. 4. BugBo 1GNAvus (Forst.). Ear-openings of medium size; nearly of the same dimensions. Osseous crest of the os sguamosum comparatively small, completely free above ; viewed anteriorly, they are almost concealed by the orbits. Posterior periphery of either orbit sharp where formed by the frontal bone. Cranium has a supermedial furrow present; its greatest height is posterior to the orbits. Jugal linear. Vomer present. Supraoccipital foramen present. To this, the second group, belongs Bubo zgnavus, which is further characterized by possessing a symmetrical cranium, and the lack of dermal ear-flaps, but in this species the first evi- dence of asymmetry exhibits itself in an insignificant differ- ence in the size of the two ear-openings. Here the cranium has a structure most like Wyctea scandiaca, and has, as in that species, powerfully developed mandibles, a conspicuous median furrow on the supero-external aspect of the cranium, broad and prominently outstanding orbital wings, markedly capa- cious orbits, and feebly developed osseous crests on either os Squamosum. Owing to the feeble development of these processes we may infer that the sense of hearing in this owl is comparatively less acute than it is in any other North-European species. The similarity in the structure of the cranium in these two species is, upon the whole, so close that doubtless they would have both been relegated to the same group had not the right ear-opening in B. zguavus been a little larger than the left, a state of affairs that I have not been able to demonstrate with certainty in the case of Vyctea. No. I.] THE CRANIUM IN THE OWLS. 125 Group III. Lar-flaps present. Cranium symmetrical. Ear- openings asymmetrical, resembling a gill-slit, but the aural skin-flaps of equal size. 5. ASIO ACCIPITRINUS (Pall.). 6. Asio oTus (Linn.). Auricular fissures or slits carried high up. The entrance to the ear is on the right side below, and on the left side above an outstretched fold of the skin. Osseous crest of the os sguamosum, upon either side, meets with the frontal bone above, without any intervening notch. Viewed from in front they are wholly visible beyond the orbits. Frontal bones obliquely sculptured at the posterior margins of the orbits; the sculpturing being most marked in A. ofws. External supermedial furrow of the cranium present ; greatest vertical depth of cranium lies in the postero-orbital plane. Jugal linear. Vomer present. Supraoccipital foramen generally found. The third group contains the two species of Aszo, viz. : A. accipitrinus and A. otus. In the case of these also is the cranium symmetrical, while the auricular openings and their dermal appendages exhibit in their structure a very remarkable asymmetry. The apertures to the ears are so markedly wide that they remind one of gill-slits, inasmuch as they extend from the nether side of the mandible, upon either side, up to a point near the middle of the forehead, where they are sepa- rated only by a small interval of space. Upon either side of this long slit-like aperture there is a raised fold of skin, the two resembling a pair of lids, of which the supero-anterior one is the real ear-flap. Crossing the aperture is an elevated fold of skin, and it is in its neighborhood that the asymmetry is especially observable. To its left side, and above it, we find the entrance to the ear, while on the right side of the head it lies below this fold. So far as the cranium itself is con- cerned it does not exhibit any special asymmetry. The osseous crests of the squamosal bones are peculiar in form, inasmuch as they ascend up to the frontal, upon either side, without any intervening notch, whereby they are endowed with an unusual amount of superficial surface, and with great depth; this, taken in connection with the unusual development of the external ear-openings, accounts for the sense of hearing having attained to its greatest acuteness in this group. The 126 SHUFELDT. [VoL. XVII. difference in the cranium of the two species is not very marked, it being confined principally to the oblique osseous plane formed by the frontal, upon either side, that extends to form the posterior periphery of the orbit. This is greater in A. otus than in A. accipitrinus. Group IV. Larflaps present. Cranium symmetrical. Auritc- ular openings reniform in outline, and the earfiap largest upon the right stde. 7, SYRNIUM ALUCO (Linn.). Auricular openings wide, carried high up, and with broad ear-flaps. Osseous crest on os sguamosum completely free above. Viewed anteri- orly, they are almost concealed by the orbit upon either side. Posterior periphery of orbit, where formed by the frontal, rounded. Median furrow present upon superior aspect of cranium; and the greatest depth of the latter is at a point just over the center of the orbit. Jugal linear. Vomer rudimentary. Supraoccipital foramen present. In Syrnium aluco, which belongs to the fourth group, the cranium, ear-openings, and ear-flaps are constructed upon a very different type as compared with the other species. We find the cranium still symmetrical ; but the auricular openings, which are slit high up, and are reniform in outline, are larger upon the right side. The same obtains with the broad, almost door-shaped ear-flaps, the form of which is somewhat different upon either side of the head. To this group also belong the other two North-European species — S. wvalense and S. lapponicum. In them the cra- nium is alike in form, and the auricular openings and the ear- flaps are as they occur in S. aluco. In these species, however, the asymmetry is extended even to include the cranium, while in S. aluco the cranium is perfectly symmetrical. S. aluco has the margins of the frontals evenly rounded where they go to form the posterior peripheries of the orbits, and the hinder part of the cranium is prettily dome-shaped, with a conspic- uous, nail-like, anteriorly projecting process upon either os sguamosum. The thinner part of the interorbital septum, which until now has been comparatively thick, is beginning No. I.] THE CRANIUM IN THE OWLS. 127 to be less extensive, inasmuch as the orbits themselves are, comparatively, not very large. Group V. Ear-flaps present. Cranium asymmetrical upon right side. Auricular openings reniform in outline, and, as in the case of the ear-flaps, largest upon the right side. a. Crania with slight asymmetry. 8. SYRNIUM URALENSE (Pall.). Auricular openings wide, carried high up, with broad ear-flaps, with the difference between the two flaps not as marked. Osseous crest on os sguamosum completely free above, more conspicuously bent forwards upon the right than upon the left side, though without coming in contact with the posterior surface of the alisphenozds in either case. Frontal bones rounded at the posterior margins of the orbits, with a deep concavity behind either supraorbital process. Longitudinal median furrow present upon the superior aspect of the cranium, and the greatest height of the latter is situated somewhat posterior to the middle of the orbital cavity. Interorbital septum quite thick. Jugal linear. Vomer rudimentary. Supra- occipital foramen absent. 6. Cranium decidedly asymmetrical. 9. SYRNIUM LAPPONICUM (Hunt.). Ear-openings wide, slit high up, and with broad ear-flaps. Asymmetry slight. Osseous crest on os sguamosum normal on left side, conspicuously individualized. Osseous crest on right side has its supero-external angle inclined forwards and codssified with the posterior margin of the alisphe- noid, which is strongly developed laterally. Frontal bones completely rounded off at the posterior borders of the orbits, and with a profound notch posterior to the supraorbital processes. Cranium with a longitudinal median furrow on its superior aspect, and the greatest depth of the former is posterior to the orbits. Interorbital septum short and thick; orbital diameter comparatively small. Jugal linear. Vomer rudimentary. Supra- occipital foramen absent. The fifth group, which, as above noted, is closely related to the fourth, and contains the two other North-European species of Syrnium, is characterized by having the cranium as well as the auricular openings and ear-flaps asymmetrical. So far as the two last-named parts are concerned, they have a structure 128 SHUFELDT. [VoL. XVII. similar to what occurs in S. al/uco, but the difference between the two sides is, strangely enough, upon the whole, less decided than in the last-named species, although always noticeable. It is here likewise that it is the right side wherein the auricular openings and ear-flaps are the larger. The asymmetry of the cranium is similar in either species, owing to a peculiar struc- ture of the right osseous crest of the os sguamosum, which is the case in a more marked degree in S. lapponicum than it is in S. wvalense. In the last-named species the asymmetry is but feebly pronounced, although always present ; the osseous crest of the os sqguamosum is somewhat more produced for- wards upon the right side, but nevertheless does not quite come in contact with the hinder border of the alisphenoid. On the other hand, this is the case in S. /apponicum,; the osseous crest is more lofty and wider, and extends its superior margin quite to the above-named bone, with which it coésifies. At the same time the entire right side of the head is more drawn out laterally, and exhibits a greater vertical compres- sion than it does upon the left side, and this is especially to be observed when the cranium is viewed upon its anterior aspect. In both these species the orbital cavity is compara- tively small, and the interorbital septum low and thick, which is especially the case in S. lapponicum. In the last-named species the cranium is, upon the whole, smaller as compared with the beak than it is in any other species, and this, notwithstanding the fact that the beak is not very powerfully developed, as it is, for example, in Budo and Vyctea. Group VI. Lar-flaps present. Cranium decidedly asymmet- vical. Auricular openings wide, uniform in size, and together with the ear-flaps exhibiting an asymmetry agree- able with that of the cranium. 10. NycTALA TENGMALMI (Gmel.). Auricular openings very wide, with crescent-formed ear-flaps; Asym- metry of aural entrance agreeing with that of the cranium. Osseous crest of os sguamosum large, deep, and distorted upon both sides; especially N@nT:] LHE CRANIUM IN THE OWLS. 129 lofty upon the right side, and situated far posterior to the orbit ; on the left side greatly compressed, and comes in contact with the hinder margin of the orbit above. Anteriorly, both osseous crests are produced as long, forward-projecting processes ; that on the right side meets the posterior border of the orbital crest of alisphenoid, and on the left is deflected, so as to come in contact with the mandible. Medio-longitudinal furrow exists upon superior aspect of cranium ; the skull’s greatest depth being post- orbital. Jugallinear. Vomer rudimentary. Supraoccipital foramen present. In the last group, which is created to contain WVyctala teng- malmt, the cranium sees its greatest asymmetry, as this asym- metry occurs in the left as well as in the right side. It is here also that the os sguamosum with its osseous crest exhibits its maximum amount of anomalous development. On the right side the osseous crest is lofty, approaching the same plane above in which lies the superior contour line of the head. On the left side it is as decidedly drawn downwards, and with the tongue-like process on the osseous crest likewise so markedly inclined in the same direction that the apex of the latter is in direct contact with the lower jaw —a condition which is per- haps unique for this genus in the class Aves. I have already availed myself of the opportunity to point out the cranial asymmetry in JV. tengma/mz in an article that has since appeared in the Proceedings of the Zoological Society of London for 1871, p. 739, entitled ““On the Asymmetry of the Skull in Strix tengmalmi”’ (it having been sent in June of the same year); and also in Vzd. Selsk. Forh. Chria., p. 68, 1872. Auricular openings are broad and wide, and have a depth equal to that of the head; both these and the ear-flaps, which are not very broad, are of the same dimensions upon either side, other- wise they present no asymmetry other than that which pertains to the cranium itself. Apart from the asymmetrical structures seen in the latter, it is perhaps most like that part of the skel- eton in Syruium aluco, and has, as in that species, a notably wide interorbital septum, part of which is transparent, and a uniform convexity of its posterior aspect. The three resident species occurring in south and middle Europe, vzz., Strix flammea (Linn.), 1766, Athene noctua (Retz), 1800, and Scops giu (Scop), 1769, together with Aszo capensis (Smith), 1835, which occurs as a straggler in the 130 SHUFELDT. [VoL. XVII. countries about the Mediterranean, are not found in Norway. The two first-named species have been found as far north as Jutland and the southern part of Skaane, but are, like Scops giu, principally south and middle European forms. Aszo capensis belongs to the Ethiopian region. I have not had the opportunity to examine the heads of any of these in the flesh; and, as the dermal structures of the auricular openings cannot with entire safety be described from dried or steamed heads, the following remarks will have reference only to the cranial characters in these species. Strix flammea, which is the type of the first subfamily of Striges, belongs, as is well known, toa special group, different from the other six groups of North- European Bubonine just described. Its principal characters are a symmetrical cranium, and a broad ear-flap, which is much larger than the comparatively small (symmetrical ?) ear-open- ings. The cranium, which appears to be entirely lacking in asymmetry, is peculiarly lengthened, with a long and slender mandibular portion, and with a marked development of the dipléic tissue in several of the cranial bones, to an extent not approached by any of the other North-European species. As in Syrnium lapponicum, the forehead slopes conspicu- ously downwards, but here, to such a high degree that the line becomes almost concave. The medio-longitudinal furrow on the top of the cranium is deeper than it is in any of the other groups, and the forehead is raised almost pyramidically above the orbits upon either side of this deep median furrow. No distinct fossa stands between the crest upon the os sqgua- mosum and the parietal bone, as is seen to be the case in most of the other groups of Bubonine, and this crest has, upon the whole, no extraordinary or very pronounced development ; but the cranium is especially remarkable on account of the great thickness of the interorbital septum, which here presents no point where it is thin, as is the case in all the other species. The orbits, relatively speaking, are notably incapacious; the lacrymals are disproportionately large and swollen, and are found beneath the frontal, upon either side, and not as in the subfamily Bubonine, partly (or often quite) beneath the supe- rior mandible. Nor T.| THE CRANIUM IN THE OWLS. I31 Finally, it may be said that the mandible is markedly wid- ened beneath the ramal vacuity; that the pars plane of the mesethmoid are thick and swollen at their apices, and widely spread out ; that the palatine bones are narrow, and the vomer well developed and mesially swelled ; and, lastly, the large orbital wings of the alisphenoid are so long that they almost reach the linear os jugale. Taking into consideration the depression of the cranium, its small orbits, and the marked development of the dipldic tissue in all the bones, Stvzx flammea, of all the North-European spe- cies of owls, stands nearest to Syruzum lapponicum, though in the latter the interorbital septum is very far from being as thick as in Strix flammea, and the lateral processes of the ethmoid are not swollen at all. Upon the whole, then, when taking into account the struc- ture of the cranium in Strzx flammea, although this exhibits no asymmetry, this form occupies an isolated place among the owls, and these peculiarities of its cranium, when taken in connection with the characters obtained from the structure of the sternum and furcula, doubtless contribute towards sustain- ing the opinion of placing this form in a separate sub- family. As far as the auricular openings in Strix flammea are con- cerned, they are small or of medium size, and probably sym- metrical (or very little asymmetrical). The ear-flaps, which are both superiorly and inferiorly squarely truncated, and are about as broad as they are high, give them, upon the whole, a resemblance to the right ear-flap in the Syrvnzum group ; on the other hand, these ear-flaps are larger than the apertures they are intended to cover, and consequently they overlay the auricular margins. Further, we observe the characteristic long and broad fold of skin, overgrown with stiff feathers (the veil), which stretches, as an oblong semi-arc, from the base of the superior mandible above the eyes, down behind the ear-open- ing upon either side, from thence quite out to the symphysis of the lower jaw. This fold of skin corresponds to the verti- cal fold that surrounds, posteriorly, the slit-like ear-opening in the genus Aszo. 132 SHUFELDT. [VoL. XVII. That Athene noctua is doubtless especially closely related to the genus Swrnza can plainly be discerned from the structure of the cranium alone. It appears that Kaup, in a paper (Zvans. Zogl. Soc., Vol. IV) to which I have not had access, has shown that Athene noctua presents an asymmetry (although slight) in the development of these dermal structures. This asymmetry cannot, with cer- tainty, be pointed out in a dry head that I possess, but in any case must have been very slight. They are of medium size, or relatively of about the same size as in Survnza funerea, with the flap absent. The cranium itself, which is symmetrical, agrees in its main characters with the cranium in the last-named spe- cies. The jugal bone is furnished with an elevated process ; the osseous crest of the os sguamosum resembles that struc- ture as it occurs in Surnia funerea; but the greatest resem- blance to this species is especially exhibited in the slender, spine-like supraorbital process, which goes far towards making clear the affinity these forms have with the diurnal birds of prey (of the genus Astur); this also extends to the structure of the cranium in these two species. In this particular the genus A¢hkene comes nearer to the genus Surnia than to Glaucitdium,;? on the other hand, it is unlike both in possessing an evident median furrow. Scops giu has also relatively small or medium-sized auricular 1 Kaup’s figure appears in A History of North-American Birds (Baird, Brewer, and Ridgway), vol. iii, p.97. Boston, 1874. In this connection compare the pterylography of the so-called “ Burrowing Owls” of the American continent, reference being made to one of them in my memoir entitled “ Notes on the Anatomy of Speotyto cunicularia hypogoea” (Journ. Morph., vol. iii, No. 1, June, 1889, pp. 115-125, Pl. VII), also in a very excellent paper by Mr. Hubert Lyman Clark, entitled ‘“ The Pterylography of cer- tain American Goat-suckers and Owls,” Proc. U.S. Mat. Mus., vol. xvii, 1894, Pp. 551-572. Many figures in text. The comparison of the feather-tracts of Speotyto and Athene would be especially interesting. — R. W. S. 2 The supraorbital processes are also spine-like and well developed in Sfeotyto, as may be seen in my figures of the skeleton of that species (Aud/. U. S. Geog. and Geol. Surv. of the Terr. Dept. of the Interior, vol. vi, No. 1, Washington, Feb- ruary, 1881, Pls. I-III), but they are quite rudimentary in Micropallas whitney, one of the smallest owls in the world, and belonging to a genus related to Glauci- dium. Speotyto, Glaucidium, and Micropallas all possess the elevated process upon the jugal.— R. W. S. Nos. I.) THE) CRANIUM IN THE OWLS. 133 openings that are lacking in dermal coverts. The structure of its cranium makes it clear that it belongs to a different type as compared with the other North-European species, even if it does appear in one of the first two of the above-arrayed groups. The cranium, which is symmetrical, has the osseous crest of the os sguamosum terminating in a pointed process, that almost comes in contact with the hinder margin of the alisphenoid, and to which it is united by ligament. Therefore the structure of this crest corresponds to what we find in the right side of the cranium in Syruium lapponicum. The aural entrance is contracted, quite slit-like, on account of the fusion of the crests with the posterior orbital margin. As to the remaining characters it may be said that the cra- nium’s greatest depth is found to be at a point situated unusu- ally far forwards, almost in the region of the supraoccipital processes ; that the jugal is linear; vomer, rudimentary ; and the orbital cavities notably large. That these characters of the crania, and the structure of the external auricular openings, can be shown to be present toa great extent in all the species of the same genus, is probable, and the few examinations that I have had the opportunity to make of the heads or crania of non-European species have sustained this. Of the genus Vyctala, in which form the asymmetry of the cranium is most evident, there is, at this time, but a single species known that belongs to the nearctic region, vzz. — lV. acadica (Gmel.), 1788, with the exception of the circumpolar WV. tengmalmz. It is quite probable that the asymmetry seen in the former is also similarly exhibited in the last-named species. Ina note in the Proc. Acad. Phila., 1870 (p. 73), Mr. Hale Streets invites attention to the fact that a pair of crania in the collection of the Academy, which were thought to belong to Wyctala acadica, exhibited an asym- metry in their cranial structure which from the description corresponds with that seen in WV. Zengmalmi. The second species exhibiting asymmetry in its cranium, Syrnium lapponicum, is represented in the nearctic region by a related species, S. czzereum (Gmel.), 1788, which was de- scribed one year earlier than S. /afponicum. That this species, 134 SHUFELDT. [Vo. XVII. characterized in the main only by its darker plumage, will present about the same structure in the cranium as the palzo- arctic S. dapponicum, is evident.! This is further shown in two figures, which are given in Baird, Brewer, and Ridgway, A History of North-American Birds, Vol. III, pp. 99, 100. Finally, Syrnzum uralense, the third species having an asym- metrical cranium, is represented in the eastern part of the palzeo-arctic region (Japan) by a similar race or subspecies, S. rufescens (Temm. and Schl.), 1850,? which is smaller and darker in plumage than the type species, but nothing is known of the structure of its cranium. It is not improbable that there are still other species of the genus Syrnium that will furnish examples of cranial asymmetry. Of this genus, Sharpe has in his Catalogue of Birds, British Museum, Vol. II, 1875, described twenty-seven species, besides various subspecies, to which are to be added two others, old species that of late years have been transferred into this genus. I. SURNIA FUNEREA (Linn.), 1766. (Plate XV, Figs. 1-3.) Both the auricular openings and the cranium are symmetrical, flap being absent in the former. The skin-like auricular openings are of medium size, sym- metrical, and comparatively lowly situated, inasmuch as their upper edges barely ascend above the middle of the eye, the lower reaching down to about the mandible. They are evenly rounded above and below, perpendicular, and in an adult female specimen (collected in West Aker, Christiania, Nov. 12, 1881) measure 12 mm. in height and 9 mm. in breadth. There is no evidence whatever of the presence of any dermal flaps, or of any raised dermal folds about the margins. 1“ One point of note is to be observed, however, and that is, in some species of Syrnium the skull is symmetrical, while in some others asymmetrical distortion to a moderate degree is observable. Of the first condition S. xebulosum is an example, and of the latter, S. cézereum furnishes us an instance.” (Shufeldt in MSS., March 20, 1896.) —R. W. S. 2 « Referred to as Strix rufescens in the text, and S. fuscescens on the plate.” No: a.) LEE (CRANIUM LN \ LAE OVCES. 135 The zostrils are of medium size, situated low down com- paratively; their height is 3 mm. and very little more than their width, which is 2mm. A tuberous cere is situated above the nostrils. The cranium, which is quite symmetrical, attains its greatest height posterior to the orbits. The deak is short and very much curved; the mandibles, not taking into account their horny sheath, measured from the frontal bones, will enter 2.6 times into the total length of the cranium. The superior surface of the cranium is even and smooth, without any median furrow, a character which, among the North-European species, it possesses in common with G/lau- cidium passerinum The supraorbital process is, in the older individuals, espe- cially long, and is seen to be a narrow, stiletto-formed, osseous process, that is directed obliquely backwards. The forehead, posterior to the supraorbital processes, is broad, of the same breadth as is that region in front of those apophyses; that is to say, the frontal borders are very nearly parallel. Frontal bones are sharp where they go to form the poste- rior periphery of either orbit. The zuterorbital septum has its thinner, semitransparent part especially extensive; in the middle of the alzsphenoid there is a vacuity caused by non-- ossification? that in size about equals the foramen opticum. The osseous crest of the os sguamosum is completely free superiorly and juts out sharply from the cranium. It is broad- est in the middle, where it develops an apophysis, directed forwards, that conceals the posterior extremity of the quad- rate, when the cranium is viewed upon its lateral aspect. Regarding the cranium anteriorly, the osseous crests are seen in plain view standing out beyond the orbital wings (that is, the osseous crests of the alisphenoids). 1 While making this translation I have before me three skulls of adult specimens of Surnia ulula caparoch, and three skulls of adult specimens of Micropallas whitneyi. The median furrow is entirely absent in the former, but there is a slight indication of one in the skulls of A/icropallas. — R. W. S. 2 This is referred to in the following words, vzz.: “et hudagtigt parti,” which, being literally translated, means “a membraneous part.” — R. W. S. 136 SHUFELDT. [Vou. XVII. Supraoccipital (squama occipitis) has a small, round supra- occipital foramen, the size of which varies in different indi- viduals (diameter 4%-1% mm.). The jugal bone is broadest in the middle, inasmuch as its superior border develops a rather long, low, but distinct process. The pterygoid bones are slender, becoming pointed in front, where they offer but small articular facets, for articu- lation with the palatines. The palatine bones are notably broad; pars plana of the mesethmotd comparatively short, not coming out beyond the external margin of the palatine bone, upon either side, when the cranium is viewed upon its basal aspect. Vomer rudi- mentary, and present as a slender osseous spine, or (in younger individuals) completely unossified.! 2. GLAUCIDIUM PASSERINUM (Linn.), 1766. (Plate XV, Figs. 4-6.) The auricular openings, which are without flaps, are, as well as the cra- nium, symmetrical. The dermal parts of the auricular openings are small, sym- metrical, and, comparatively speaking, placed high up, inasmuch as their inferior extremities do not descend further down than the lower border of the eye, the superior extremities ascending to a point opposite the center of that organ, upon either side. They are oval in form, with the longitudinal axis, in each case, obliquely directed backwards. In an adult female specimen (collected at Lillehammer, Dec. 9, 1876) the longest diameter measured 6 mm., and the transverse diameter 4.5 mm. The flaps were absent, and the skin did not create an elevated fold about the borders. The xostrils are small, with a comparatively broad space between them, and are directed forwards, inasmuch as they are situated in the fore part of the much swollen cere. Their ver- tical diameters slightly exceed their transverse ones. The cranium, which is symmetrical, agrees, upon the whole, 1 Literally translated this reads “fuldkommen hudagtigt,” meaning “ fully membraneous.” —R. W. S. No. 1.] THE CRANIUM IN THE OWLS. R37 with the corresponding characters as they occur in the cranium of Surnia funerea; its greatest height, as in that species, lies posterior to the orbits. The deak is short, thick, and very much hooked; the mandi- bles, not taking their horny sheath into account, measured from the frontal bones, will enter almost two times (2.8—2.9) into the total length of the cranium; thus it is shorter than in any other North-European species. The surface of the cranium is smooth, without any median furrow; the forehead, posterior to the supraorbital processes, is very slightly convex, its surface being broad behind them, but progressively narrower in front of them. The frontals form sharp borders at the posterior parts of the orbits ; the thick- ness [| fortykkelse| of the forehead in the neighborhood of the supraorbital processes is less than it is in any other species. The thin, semitransparent part of the interorbital septum is extensive; in the middle of the alisphenoid there is an unossi- fied point, that is occasionally as large as the optic foramen. The osseous crest of the squamosal agrees with what we found in Suruza funerea, and though standing well outwards, its process is less produced. When we view the cranium upon its lateral aspect, then the crest conceals from view the poste- rior extremity of the quadrate bone, and, viewed from the front, this is seen outside the orbital wings (that is, the osse- ous crests on the alisphenoids). The jugal is, as in Surnia funerea, broadest in the middle, inasmuch as its superior border develops in that region a long- ish, low apophysis; in all the other North-European species the jugal is linear. Supraoccipital (squama occipitis) has an oblong supraoccip- ital foramen, that is relatively, as well as absolutely, larger than in any other inland species (vertical diameter 3 mm., transverse diameter 2% mm.).} The pterygoid bones are somewhat broader at their anterior ends, and are there furnished with better developed articular facets for the palatines than they are in Surnia funerea. 1 Micropallas also presents this foramen, and in this species it attains a size equal to one-fourth the size of the foramen magnum. — R. W. S. 138 SHUFELDT. [Vou. XVII. The palatine bones are quite broad ; pars plane of the meseth- moitd comparatively short, and are concealed by the palatines when the skull is viewed upon its basal aspect. Vomer rudimentary, being developed only as an almost invisible osseous spicula, or, as in the younger individuals, completely unossified. The maxillo-palatines are notably small, and well separated in the median line.! 3. NycTEA sScANpIAcA (Linn.), 1766. (See Figs. 1 and 2.) The auricular openings, which are without flaps, are, as well as the cra- nium, symmetrical. The dermal parts of the auricular openings are of medium size, symmetrical, and situated comparatively low down, as their lower extremities do not pass the superior borders of the mandible, upon either side, and the superior tips ascend only about to the middle of the eye. They are evenly rounded off both above and below, with their longer axes somewhat ob- lique. In an adult male specimen (collected in Ringebo, Oct. 19, 1876) the vertical diameter is 20 mm., and the transverse diameter 11 mm. There is no evidence of any flap, but the skin on the anterior borders forms, in either case, a somewhat raised fold. The wostri/s are quite large, roundish, and placed high. Vertical diameter is 6 mm., and the transverse diameter the same. Posterior to the nostrils, the cere is very little swollen. The cranium, which is symmetrical, possesses espe- cially large orbital cavities, and its greatest height is posterior to the latter. The decak is of medium length and comparatively strong. The mandibles, not including their horny theca, measured from the frontal bones, will enter slightly more than twice (2.1) into the total length of the cranium. On its superior aspect the 1 These ossifications are also comparatively small in Micropallas whitney, and owing to the relatively as well as absolutely shorter superior mandible in this pygmy species, these spongy masses of bone are brought closer together medi- ally; indeed, they come very near being in contact. —R. W. S. No. 1.] THE CRANIUM IN THE OWLS. 139 cranium has a longitudinal median furrow, which is especially well marked in the region of the base of the superior mandible, and between the parietal bones. The supraorbital processes are situated comparatively far forwards (anterior to the middle of the orbits). The forehead, posterior to the supraorbital processes, is somewhat contracted, narrower in fact than it is anterior to these apophyses, and the orbital borders are here about par- allel to each other. The frontal bones are sharp where they form the posterior borders of the orbits ; the forehead is espe- ! Fic. 1.— Left lateral view of the skull of Nyctea scandiaca cially thick in the (Linn.) ; two-thirds natural size. region of the supra- orbital processes. The thinner, semi- transparent part of the zzterorbital sep- tum is extensive; in the middle of either alisphenotd there is an unossified area, and in the cranium of one Fic. 2. — Left lateral view of the plucked head of a specimen of the specimens BNE of Myctea scandiaca (Linn.); two-thirds natural size. (Both figures by Shufeldt, after Collett.) hand there are, more anteriorly, in the direction of the ethmoid two other minute areas of a similar character. The osseous crest of the squamosal bone is, comparatively speaking, more feebly developed than it is in the other groups. Superiorly, it terminates in a pointed process, that is directed somewhat anteriorly, which, when the cranium is viewed upon its lateral aspect, conceals from view the distal end of the os gquadratum. The broad orbital wings (that is, the osseous crests of the 140 SHUFELDT. [VoL. XVII. alisphenoids) hide those structures upon the os sguamosum of either side, when the skull is looked at from in front. The supraoccipital (squama occipitis) possesses an exceedingly small, round supraoccipital foramen (the diameter being about I mm.). The pterygoid bones are narrow both anteriorly and posteri- orly, while their upper and lower margins are sharp. Their facets for the palatines are triangular in outline. The palatine bones are of about medium width; the pars plana, upon either side of the mesethmoid, long and strong, and, when viewed from beneath, are seen to extend laterally well out beyond the external borders of the palatines. Vomer rudimentary, or else unossified (that is, in all the five specimens examined up to the present time, all of which are probably subadult individuals). In older or adult birds, ossification, to some slight extent, may take place. Mesially, the maxillo-palatines are not widely separated. 4. Buso 1GNAvus (Forst., 1817). (See Fig. 3.) The auricular openings, which are without flaps, slightly asymmetrical ; the cranium is symmetrical. The dermal parts of the auricular openings are rather large and subequal in size, inasmuch as the right one is somewhat larger than the left. They are oval in outline ; a male speci- men (collected at Western Aker, Sept. 23, 1875) has its right ear-opening measuring 30 mm. in height, and with a width of 19 mm., the left aperture possessing a height of 26 mm. and a width of 16mm. There are no ear-flaps, but the anterior border upon either side develops a slightly elevated fold of skin. The nostrils are subcircular in outline, and, as in the genus Nyctea, situated rather superiorly. The cranium, which in all its main characters agrees with the cranium in WVyctea scan- diaca, is large and coarsely constructed, being symmetrical, and with comparatively large orbital cavities; posterior to which latter we find the greatest height of the cranium to be situated. No. 1.] THE CRANIUM IN THE OWLS. I4I The deak is somewhat long and strong, the mandibles, when not covered by their horny theca, measured from the frontal bones, will enter a little more than twice into the total length of the cranium. The superior surface of the cranium exhibits a median furrow, which, as in /Vyctea, is deepest in the frontal region at the mandibular base and between the parietals. The ordzts are markedly capacious, the diameter in each being twice as long as the postorbital part of the cranium. The crest of the alisphenoid (posterior orbital process) is conspicu- ously broad and prominent above, and powerfully developed. Fig. 3. — Left lateral view of skull of Buso zenavus ; two-thirds natural size. (Shufeldt, after Collett.) The forehead is, as in Wyctea scandiaca, somewhat contracted posterior to the supraorbital processes, and the latter are situated comparatively far forwards (anterior to the middle of the orbits). The frontals, where they enter into the posterior peripheries of the orbits, are sharp; the thickening of the frontal region in the vicinity of the supraorbital processes is especially well marked. The thinner (transparent) part of the zzterorbital septum is less extensive than it is in Wyctea scandiaca, from the fact that the alisphenoid is thicker in front of the optic foramen than it is in that species, which is likewise the case with the mesethmoid element. The osseous crest of the os Squamosum is, comparatively speaking, feebly developed, but, upon the whole, somewhat stronger than it is in /Vyctea; it is, as in that genus, completely free superiorly, and develops in the margin there a semi-anteriorly directed sharp-pointed I42 SHUFELDT. [Vo.u. XVII. process, which, when the cranium is viewed laterally, conceals the distal extremity of the quadrate. Viewed from in front, they are almost completely hidden behind the broad orbital wings (that is, the osseous crests of the alisphenoids). The supraoccipital (squama occipitis) has a very minute and circular supraoccipital foramen (diameter barely I mm.). The pterygoid bones are, as in Nyctea, narrowed both before and behind, and develop cultrate margins both superiorly and inferiorly ; the articular facets for the palatines are triangular in form. The palatines themselves are comparatively slender ; the pars plana, upon either side of the mmesethmoid, long and stout, and extends far out beyond the external border of the palatine bone, when we view the skull upon its basal aspect. Vomer rudimentary, and somewhat enlarged mesially. In- feriorly, the maxtllo-palatines are separated but by a small interval of space. 5. ASIO ACCIPITRINUS (Pall.), 1771. (Plate XV, Figs. 7 and 8. — Plate XVI, Figs. 9-11.) Auricular openings and their flaps asymmetrical ; cranium symmetrical. The dermal parts of the auricular openings are asymmetrical, remarkably long, being almost level with the top of the head, and resemble gill-slits. They extend from the frontal region in a curved direction (Za/vbue) down to the nether side of the lower jaw, where they reach or even pass beyond the angle of the gape (the superior angles of these slits are separated at the vertex of the head by a very narrow interval). Their vertical height in an adult specimen (collected at Krogskoven, Oct. 16, 1876) is about 35 mm. The auricular opening, both in front and behind, is bounded by a raised fold of skin, that extends the entire length of the aperture, performing the function of the ear-flap, although the true ear-flap is here, as well as in the other species possessing it, composed of the anterior, which is at the same time the larger fold of skin. This, the true ear-flap, is crescentic in out- line (narrowing upwards and downwards), and broadest in the middle (about 12 mm. wide). While, on the whole, this ear-flap No. 1.] THE CRANIUM IN THE OWLS. 143 is symmetrical for the two sides, the tensor muscle that closes them, and which transversely divides either auricular opening at about its middle, exhibits a peculiar asymmetry. This muscle arises symmetrically on the right as well as on the left side, near the center of the lid’s inner surface, while its attachment, upon either side, to the cranium posteriorly is thoroughly asymmetrical. On the right side the tensor muscle is attached posteriorly, at a point about in the middle of the osseous crest of the os sguamosum, or rather so high up that the entrance to the ear upon this side must necessarily be below the transverse fold formed by the muscle, and that part of the entrance above the muscle consequently closed. On the left side the muscle is directed more obliquely downwards and makes an inferior attachment posterior to the mandible, at the lowest extremity of the osseous crest of the os sgua- mosum,; consequently the aural entrance is found above the muscle, while the lower part of it is closed over. The muscle’s attachment to the ear-flap, as already described above, is seen to be upon the inner surface of the latter, near its center, after first having passed and received support from the short but distinct process which occurs upon the posterior aspect of the osseous crest of the alisphenoid. In addition to the tensor muscle proper, there is a feebler one lower down, which, upon either side, passes from the mandibular border to the lid’s inner surface, in the direction of the gape of the mouth. The nostrils are oblong, elevated, close together, and com- paratively large, besides being longer than they are high (length 6 mm.; vertical diameter 4 mm.). That part of the beak posterior to the nostrils, and covered by the cere, is somewhat raised and of oblong form. The cranium, which does not exhibit any notable asymmetry, is, if viewed upon its superior aspect, seen to be strikingly pointed, or almost triangular, inasmuch as such parts of the margins of the orbits formed by the frontals are obliquely sculptured ; therefore the postorbital region of the cranium is more con- tracted, and lacks the rounding off which takes place in the other groups. The greatest vertical height of the cranium is 144 SHUFELDT. [VoL. XVII. posterior to the orbital cavities. The beak is comparatively feebly developed, being powerfully deflected from the frontal region, obliquely downward, in addition to being quite short. The mandibles, omitting their horny sheath, and measured from the frontal bones, will enter almost 2.2 times into the total length of the cranium. The cranium’s superior surface ex- hibits a median furrow that is especially well marked in the frontal region, posterior to the supraorbital processes. The orbital cavities are relatively small, due to the fact that their posterior borders, where formed by the frontal bones, are obliquely truncated; and, moreover, the alisphenoids are short and thick. The osseous crest of the alisphenoid (proc. orbit. poster.) aS we pass upwards, is seen to become rapidly nar- rower, it having its greatest width about its center; upon the broadest portion there is, on the external border, a process directed backwards and outwards, and which affords attach- ment for the superior portion of the tensor muscle that passes to the ear-flaps. This process is symmetrical upon either side, although the muscle referred to is asymmetrical at its distal extremity. The frontal region is comparatively narrow, partic- ularly so posterior to the supraorbital processes, where, indeed, it is narrower than is the part in front of them; while the orbital borders are nearly parallel to each other. The frontal bones of the posterior orbital peripheries slope obliquely away, being abruptly truncated above and below, and have a height that is somewhat less than the length of a pterygoid bone. Inasmuch as both the alisphenoid and mesethmoid are thick- ened bones, the interorbital septum is necessarily so, the only exception to this being a place just above the sphenoidal ros- trum, where the septum is seen to be thin (semitransparent). The osseous crest of the os sguamosum is not especially well individualized superiorly (by an evident and deep groove sepa- rating it from the alisphenoid), but is continuous in the upward direction without any intervening cleft, or glenoid fossa, quite up to the frontal; as the crest thus becomes somewhat long, and is likewise rather deep, and possesses a semi-anteriorly directed border, it forms a fossa, opening anteriorly, which is larger than the similar cavity seen in the other species having No. 1.] THE CRANIUM IN THE OWLS. 145 a symmetrical cranium. Therefore they are enabled to appre- ciate the least evident vibrations of sound far easier than the others, and this, moreover, becomes even still easier inasmuch as they possess, too, such conspicuously large dermal parts to their auricular openings. The external border of this osseous crest is quite even, and no process is developed upon it, and, as mentioned above, it is but slightly deflected forwards, so that it does not come quite opposite to the quadrate bone when the skull is viewed upon lateral aspect. Regarding the cranium from in front, the osse- ous crests, in their entirety, project, lateral-wise, beyond the orbital wings (that is, the osseous crests of the alisphenoids). Supraoccipital (sguama occipitis) has in some specimens a very small supraoccipital foramen, while in others the bone is not perforated at all. The pterygoid bones are, especially in front of the basiptery- goid processes (proc. pteryg. oss. sphenoid.), broad and flat, their borders being even and their distal ends presenting extensive and compressed articulatory facets for the palatines. The palatines are of medium width; the pars plana upon either side of the mesethmoid is widely spread out and, if the cranium is viewed from beneath, is seen to come out beyond the externo-lateral margins of the palatines. Vomer present ; usually, but not always, somewhat mesially enlarged. The maxillo-palatines are large and come almost in contact in the median plane. 6. Asio otus (Linn.), 1766. (Plate XVI, Fig. 12.) Auricular openings and their flaps asymmetrical ; cranium symmetrical. The dermal parts of the auricular openings agree exactly with what was found in A. accipitrinus, and the transverse fold (tensor muscle) presents precisely the same asymmetry in its posterior attachment as in that species. On the other hand, the ear-flap, as well as the corresponding posterior fold of integ- ument, is perhaps somewhat a little higher, and consequently the entrance to the ear is larger. This really insignificant 146 SHOUFE EDT. [VoL. XVII. departure agrees with such other differences as are to be found in the structure of the crania of the two species under consid- eration. The flap is 13 mm. wide, and the posterior integu- mental fold about 8 mm.; the height of the ear-slit in an adult male specimen (collected at Hamar, May 23, 1880) is, as in A. accipitrinus, about 35 mm. The nostrils, the structure of the beak, and its relation to the total length of the cranium are identically the same as in A. accipztrinus. The cranium likewise, in the main, agrees with the cranium of A. acczpi- trinus. Its pointed, triangular form is here even better marked, inasmuch as the obliquely sculptured part of either frontal is more extensive and reaches further backwards. The greatest vertical height of the cranium is found in the posterior orbital region. The superior surface exhibits the same median furrow as in A. accipitrinus. The orbits are comparatively even of less diameter than they are in A. accipitrinus, due to the fact that their obliquely sculptured portions at their posterior borders, which are contributed by the frontal bones, are, in the present species, more extensive than in A. acczpitrinus. The longitudinal diameter of the postorbital part of the cra- nium is here almost as great as is the diameter of the orbit; in A. accipitrinus it is considerably less. The osseous crest of the alisphenoid (proc. orbit. post.) is notably small and narrow ; while the apophysis upon its poste- rior surface (at least in the specimens examined by me up to the present time) is either rudimentary or absent. The frontal region is somewhat broader than it is in A. accipitrinus ; its width is greater posterior to the supraorbital processes than it is in front of them, while the reverse of this is the case in A. accipitrinus. The frontals form at the posterior borders of the orbits, as in A. accipitrinus, a slanting surface, which is abruptly trun- cated both above and below; but this surface is deeper than in the species named, inasmuch as its height is equal to the length of a pterygoid bone. The interorbital septum is transversely thick, as in A. accipitrinus, and, as in the species named, No. I.] THE CRANIUM IN THE OWLS. 147 exhibits only a single, limited, thin (semitransparent) area just above the sphenoidal rostrum. The structure of the osseous crest of the os sguamosum cor- responds exactly with what was found in A. acczpitrinus, but, inasmuch as the truncated portion of the frontals posterior to the orbits is more extensive than it is in that species, and the big orbital wings (on os alisphenoides) being, as a consequence, situated further forwards, the distance between the osseous crest and the orbit is greater, and the fossa thus created, more capacious, particularly above, than A. accipitrinus. The supraoccipital (sguama occipitis) is pierced by an ex- tremely minute supraoccipital foramen, which, as in the spe- cies just mentioned, is situated at the base of a little oblong fossa, and in some individuals it doubtless will be found to be absent. The pterygoid bones seem to be somewhat narrower than they are in A. accipitrinus and offer a less extensive articular surface for the palatines than in that species. The palatine bones are perhaps a little broader than in A. accipitrinus,; pars plana of the mesethmoid barely passes beyond the external border of the palatine, upon either side, when the cranium is viewed upon its nether aspect. Vomer present, and developed as in A. accipitrinus. The maxzillo-palatines are large and come near being in contact in the median plane of the skull. 7. SYRNIUM ALuco (Linn.), 1766. (Plate XVII, Figs. 13, 14. — Plate XVIII, Figs. 17-20.) Ear-openings, as well as the ear-flaps, asymmetrical ; the cranium sym- metrical. The dermal parts of the auricular openings are of subequal size, and they possess asymmetrical flaps. These openings are, upon the whole, wide; their borders giving them a reniform, or oblong bean-shaped, outline; on the right side, where the 1 While this translation was being made, I have had before me a complete skeleton of Asio wilsonianus (Asio Brisson; Strix otus Linn.), collected by me at Fort Fetterman, Wyoming, in April, 1881, and I find the characters it presents agree, in so far as the skull is concerned, with the corresponding ones so correctly given above by Professor Collett for Asio otus. —R. W. S. I 48 SHUFELDT. [VoL. XVII. aperture is the larger, it has, in an adult female specimen (col- lected at Aker, Nov. 10, 1876), a height of 25 mm. and a width of 12-13 mm. ; the entrance is smaller upon the left side, and has a height of 22 mm. and a width of 11-12 mm. Compara- tively speaking, they are situated rather high up, inasmuch as their lower extremities do not fall below the inferior arc of the eyeball, upon either side. Superiorly, the right opening passes above the eyeball; the left being situated a little lower down than this. The distal border of an ear-opening is bounded by a thickened integument, approaching in its nature a low, free fold of skin. The ear-flaps are also asymmetrical. On the right side, where the aperture is the larger, it is broad, being squarely truncated both superiorly and inferiorly, and has an average width of about 12 mm.; on the left side the flap nar- rows as it ascends, but below is carried out as an irregular, inferiorly directed point; in this locality the flap sees its great- est breadth, being about 11-12 mm. The nostrils are markedly small, elevated, and almost circular; their diameter, in either case, being about 2mm. The cranium, which is symmetrical, is comparatively large, and the posterior region is prettily dome-shaped ; its greatest vertical height being comparatively far forwards, that is to say, about over the middle of the orbits. The beak is of medium size, with flattened sides; the mandi- bles, measured from the frontal bones, not taking into consid- eration their horny covering, will enter 2.3 times into the total length of the cranium. The superior aspect of the cranium has a longitudinal, median, shallow furrow that becomes more distinct in the frontal region between the supraorbital processes. Posterior to the supraorbital processes the frontal region is notably broad, and considerably (sometimes almost double the width) broader than the forehead is in front of the processes. The latter diminishes rapidly in width as one passes anteriorly, and, when the cranium is viewed from above, it is seen that 1 At this writing I have at hand the skeleton of a specimen of Syrazum nebu- losum, a ‘bird of the year,” collected by me at New Orleans, La., in July, 1883. In it the furrow, as usually seen in owls on top of the cranium, is replaced by a sharp, linear, deep-seated crease that is distinctly carried from the base of the superior mandible to the supraoccipital prominence behind. —R. W. S. INO.) THE CRANIUM IN THE OWLS. 149 here the lateral borders are quite concave. Where the frontals enter into the formation of the posterior peripheries of the orbits their borders are rounded off ; and, if we view the skull from behind, the supraorbital processes are concealed from sight by the vertex of the cranium. The thinner (transparent) parts of the wall of the inter- orbital septum are quite extensive. The osseous crest on either squamosal bone is of medium size only. Above, it is completely free, and there develops a curved process, directed forwards and upwards, which, when the cranium is viewed lateral-wise, is seen to be opposite to the posterior border of the quadrate. Regarded from in front, it is only their outside edges that become visible to the outer side of the large orbital wings (that is, the osseous crests on the alisphenoids). An extremely minute supraoccipital foramen pierces the supraoc- cipital bone (sguama occzpitis), the diameter of which in the subadult individuals is equal to about 1 mm., while in the older birds it is barely more than % mm. Anterior to the basipterygoidal processes (proc. pteryg. oss. | sphenoid.) either pterygoid is compressed from above down- wards, having a uniform width, and with its cultrate edge directed anteriorly. The palatine bones are quite broad; the lateral processes of the os ethmoides pass outwards so as to be about opposite the external margins of the palatines, when we regard the cranium from beneath. Vomer is rudimentary, as only its posterior moiety ossifies as a minute spicula of bone; ossification not being extended to its anterior end. It is very likely that in still younger individuals it does not ossify at all. The maxillo-palatines are of unusually large size and come very near being in contact in the middle line, below. 8. SYRNIUM URALENSE (Pall.), 1776. (Plate XVII, Figs. 15, 16; Text-fig. 4.) Auricular openings and their flaps asymmetrical, the cranium slightly asymmetrical. The dermal parts of the auricular openings are of subequal size, with a somewhat asymmetrical lid; upon the whole, 150 SHOFELDT. [VoL. XVII. these structures agree with the corresponding ones as they occur in S. aluco, only being relatively a little smaller. -The auricular openings may be said to be quite wide, and have a reniform outline. On the right side, where the opening is the larger, it has, in an adult specimen (collected at Lojten, Nov. 1, 1881), a vertical height of 26-28 mm. and a width of about 14mm. The aperture upon the left side is somewhat smaller, the height being 23 mm., the width about 14 mm. Comparatively speaking, they are placed pretty well up on the side of the head, inasmuch as on the right side the lower end descends to a point slightly below the inferior arc of the globe of the eye; superiorly, they are carried up, upon either side, to a point in the same plane with the top of the eyeball. The hinder border of either auricular opening is, as in S. aluco, bounded by a thickened fold of integument, infe- riorly. An asymmetry of the ear-flaps, also agreeing with what we find in S. aluco, is present; on the right side, where the aperture is the larger, it is broad ; both above and below it is transversely truncated, and, upon the whole, has a consider- able breadth, which corresponds in size to that of the ear- opening. On the left side the flap is somewhat irregularly drawn downwards, and terminates in a shorter projection, though it still agrees with what we find in S. aluco. The nostrils are of medium size, oval, and with their breadth and height about equal (nearly 4mm.). The cranium, which is almost but not completely symmetrical, is, in its main char- acters, like the cranium of S. a/uco, although the mandibular portion is more powerfully developed as compared with the cranium, and the orbits are comparatively smaller. The asym- metry, to which reference has been made, and which is almost imperceptible, is due to the fact that the osseous crest of the squamosal bone is inclined slightly more forwards upon the right side than it is upon the left, thus foreshadowing the very decided asymmetry which will be found to be present in these structures in S. lapponicum. The greatest vertical height of the cranium is at a point posterior to the orbital cavities. The bill is moderately long, though not of a powerful build; it will enter twice into the total length of the cranium, measur- No. 1.] THE CRANIUM IN \ THE. OWLS. I51 ing from the frontal bones, and not including the horny theca that covers it. Upon the superior aspect of the cranium there is a very distinct median furrow, which, in the three specimens examined, is best marked at the cranial vertex in the inter- parietal region. The orbital cavities are comparatively smaller than they are in S. aluco, inasmuch as the os alisphenoides is here shorter and thicker. Taken upon the whole, the orbital diameter is of about the same length in the two species. The big orbital wings (the osseous crests of the alisphenoids) are in both these owls comparatively broad and large. The frontal region, posterior to the supraorbital processes, is conspicuously wide, and even much wider than it is in front of them, where it gradually narrows anteriorly, but not in as marked a degree as it does in S. aluco. The frontal bone is, upon either side, thoroughly rounded off where it forms the hinder border of the orbit, but it is seen to slope obliquely away in the direc- tion of the large orbital wing, so that we are enabled to see the supraorbital processes when the cranium is viewed upon direct pos- terior aspect. The zxterorbital septum is quite thick transversely, inasmuch as both os al- Sphenotdes and os eth- motdes enjoyasimilar con- dition throughout all their parts; as in Aszo there is only a localized area, situ- ated above the rostrum of the sphenoid, where the Fic. 4. — Cranium of Syrnzum uralense, seen from above, septum is thin and semi- and showing slight asymmetry of the crests of the os transparent. The osseous squamosum ; compare this with same view of cranium of S. lapponicum. (Adapted by the author from Collett.) crest of the os sguamosum agrees entirely with what was found in S. a/uco, being an out- standing, nail-like, and superiorly free process; but at the same time it exhibits in the slight forward inclination of its anterior 152 SHUFELDT. [VoL. XVII. border of the right side, as has already been pointed out above, a disposition to approach the asymmetry which is present in S. lapponicum. The difference seen in the two sides is better marked in the crania of some specimens than it is in others, and can in the adult individual vary between 1 and 2 mm., this differ- ence being interesting rather than remarkable, inasmuch as it is just here that in S. /appontcum such decided asymmetry is present. This difference can best be appreciated when the cranium is viewed from above (see Fig. 4), although even then it is seen to be very slight, though it is invariably present. The occipitale superius (squama occipitis) has no supraoccip- ital foramen. The pterygoid bones are, as in S. aluco, broad in front of the basipterygoid processes, and quite compressed. The palatine bones are, comparatively speaking, narrower than in S. aluco; pars plane on os ethmotdes reach a little beyond the outer margin of either palatine, when the cranium is viewed from below. Vomer is almost rudimentary, inasmuch as it is present only as a thin osseous spicula posteriorly, and non-ossified in front. Maxillo-palatines are very large, and meet in the line below. 9. SYRNIUM LAPPONICUM (Thunb.), 1780. (Plate XIX, Fig. 27; Plate XX, Figs. 28-30. Text-figs. 5-7.) Auricular openings ; ear-flaps; and cranium asymmetrical. The dermal parts of the auricular openings, structurally, about agree with the two other species of Syruzum and present a similar asymmetry. Upon the whole, they are quite large, being subequal in size, although this asymmetry is apparently less than in S. aluco. Upon the right side, where they are of the greater size, the ear-opening has in an adult female specimen (collected in East Aker, Nov. 17, 1881) a vertical height of 30 mm. and a width of 15 mm.; on the left side the height is 28 mm. and the width 14mm. They may be said to be placed high up on the side of the head, being situated just back of the No: 1.) TAECRANIOM TN TIPE OWLS. 153 eyes, and consequently their upper and lower ends (more par- ticularly upon the right side) extend slightly past the ees: and lowest points in the eyeball. The distal border in either auricular opening is surrounded by a thick and somewhat raised fold of integument similar to what is found in the other species. The flaps are large and somewhat asymmetrical, though in a less degree than in S. aluco. The flap is larger on the right side, and has a length that somewhat exceeds that of the ear-opening, being about 35 mm. The width is 17 mm., and this flap is less obliquely truncated than it is upon the left side; its lower end is, transversely, quite straight. The ear-flap is, upon the left side, greatly narrowed above and broadest below, where it forms a long, produced, and deflected extremity. The length and breadth of this flap do not materially differ from the same measurements given for the right side. Across either auricular opening there is stretched a fold of skin or tensor muscle! that is attached at a point somewhat above the middle of the lid; on the right side this arises from the tuberous and comparatively inferiorly situated superior border of the osseous crest of the alisphenoid (or the large orbital wing); on the left side this tubercle is found higher up and less prominent, and the tensor muscle passes this, its origin being found upon the posterior aspect of the osseous crest of the squamosal bone, at its superior extremity. Owing to the formation of the cranium, the entrance to the ear, or the canal leading from the same to the parts within, has a different direction upon the two sides. On the right side this canal passes almost directly into the cranium immediately be- neath the tensor muscle of the ear-flap; on the left it passes obliquely downwards beneath the muscle. The zostrils are comparatively large, elevated, somewhat oblong ; their longitudinal diameter is 7 mm., the height 5 mm. The cranium, which is asymmetrical, resembles in its struc- 1] presume Professor Collett means the “tensor muscle,” the same having the appearance of a “fold of skin.” It reads in the original “Strekker sig en Hud- fold eller Lukkemuskel.” To be sure, the muscle is included within a fold of skin. — R. W. S. 154 SHUFELDT. [VoL. XVII. ture the cranium in Syruium uralense, but in it the mandibular parts are more powerfully developed ; the parietal region is more pyramidal in contour, and with comparatively smaller orbits than in that species. The cranium sees its greatest height opposite the posterior margins of the orbits. The asymmetry is chiefly due to the somewhat distorted develop- ment of the osseous crest of the right os sqguamosum. The beak is laterally compressed, but is not especially strong; the mandibular portion has a greater length than in any other inland species, and does not quite enter twice (1.9) into the total length of the cranium, ie.) epee earn not taking into account its horny, Skull seen from in front; mandible at- integumental theca. The median eee natural size. (Shu furrow upon the superior aspect of the cranium is quite well marked its entire length, being especially so in the frontal region, posterior to the supraorbital processes. The orbit has a comparatively less diameter than in S. wvalense, inasmuch as os alisphenoides is notably short and thick, which is likewise the case with that part Fic. 6.— Syrnium lapponicum (Thunb.). . ; Skull seen from behind; mandible at- of either frontal which forms the tached; two-thirds natural size. (Shu- margin of the orbit superiorly i - feldt after Collett.) k The supraorbital processes are situated far back, so much so that their apices, upon either side, reach to a point upon the orbital crest of the os alisphe- noides. Further, either one of these processes is very broad, and develops as a long frontal extension, which is connected by a membrane with the tubercle of the orbital wing, superiorly, and in this manner contributes towards the formation of the hinder roof of the orbital cavity. The osseous crest of the alisphenoid (frocessus orbitalis posterior) is on the right side somewhat asymmetrical, as is No. 1.] THE CRANIUM IN THE OWLS. 155 also the os squamosum, inasmuch as it is here drawn out in a greater degree laterally, and also more depressed than upon the opposite side, in such a manner that the crest becomes broader above, on the right side, and more tuberously swollen than upon the left side. The orbits thus become a trifle wider, but at the same time lower, than upon the left side. Upon the posterior aspect of the apex of the osseous crest there is to be found a process that is not especially conspicuous. The frontal region, posterior to the supraorbital processes, is profoundly concaved,! but, upon the whole, particularly broad, and much broader than the surface in front of these processes, which, relatively speaking, is also of considerable width. Either frontal bone slopes obliquely downwards from the middle of the cranium towards the hinder border of the orbit, and is very deep posterior to the supraorbital processes. If the cranium is seen upon direct posterior view, the supra- orbital process of the right side, including its upper border, is in view beyond the limiting profile line of the frontal, while the left one is hidden behind it. The interorbital septum is notably thick and of limited area, and this thickness is to be found over its entire extent, and it is only just above the rostrum of the sphenoid that there is to be found a thinner place, which only in a very limited degree is semitransparent. The osseous crest of the squamosal bone is normal upon the left side, having the same structure as in S. a/uco and S. uralense, forming there a supero-anteriorly directed process, that is, above, perfectly free. This crest is particularly lofty upon the right side, where it extends upwards and forwards as a prominently curved apophysis that reaches to the upper border of the os alisphenoides; this latter is decidedly massive, and, as has before been remarked, stands out from the side of the skull in a most abnormal manner. The two processes do not fuse at their point of contact, but are simply joined there by membrane. The fossa formed by the osseous crest, the entrance to which is in front, thus becomes more capacious, and 1 I take this to refer to the superior orbital borders, they being roundly concaved in most species of Syrzium, just behind the supraorbital processes. — R. W. S. 156 SHUFELDT. [Vou. XVII. especially more lofty than upon the left side. Regarding the cranium upon its anterior aspect, it will be seen that the promi- nent orbital wing completely conceals from view the osseous crest of the right squamosal, while upon the left side the ex- ternal border comes into sight beyond the orbital wing. Upon the whole, the asymmetry of the cranium in this species can best be appreciated by viewing it from above; while thus seen, one can also more easily compare the powerfully anteriorly directed superior bor- der of the osseous crest of the right side with its retreating border upon the deft: | (ee Fig. 7.) Supraoccipital (sgua- ma occipitis) lacks, as in S. uvalense, a supra- occipital foramen. The pterygoid bones are more slender than in) S:/ alaco: andi uvalense, and possess smaller articular facets Fic. 7.— Cranium of Syrxium lapponicum seen from above, i i ; and showing the degree of asymmetry of the squamosal for articulation with on Sere aie Me of ee thie) pala ea aa paratively speaking, the palatine bones are especially slender ; the lateral processes of the ethmoid are well developed, and have an unusually high point of origin, being upon a level with the olfactory foramen, or slightly below the superior border of the lachrymal bone, upon either side; they are widely spread out, and when the skull is seen from below, nearly the whole of either one of them can be seen beyond the external border of the palatine of the same side. The vomer is, as in other species of this genus, nearly rudi- mentary, as it is only represented posteriorly by a minute osseous spicula, being otherwise unossified (in subadult indi- viduals, perhaps entirely so). No. 1.] THE CRANIUM IN THE OWLS. 157 The maxillo-palatines are unusually large, and are in contact in the mesial plane, below. 10. NycTALA TENGMALMI (Gmel.), 1788. (Plate XIX, Figs. 21-26.) Auricular openings and flaps asymmetrical ; the cranium profoundly so. The dermal parts of the auricular openings are nearly of equal size upon the two sides, but in other respects exhibit an asymmetry that agrees with the asymmetry assumed on the part of the cranium itself; they are very large, occupying as they do the whole side of the head, upon either side ; they are somewhat semilinear or oval in outline, but less pointed above and below than in Aszo, and therefore not as gill-slit-like as in that genus. Their vertical height in an adult specimen (collected at Hamar, Sept. 20, 1876) is about 28 mm., the greatest inner width being about 12 mm.; but they frequently have a greater width than this. Hither of these openings extends from beneath the mandible or lower jaw (close to the mandibular commissure) up to the side of the frontal region, where the space separating the one from the fellow of the opposite side is comparatively wide, being but a little less than the height of either ear-opening. The ear-flap that closes the aural aperture in front is of a semi- lunar outline, but is not very broad, as at a point opposite the center of the eyeball it barely exceeds 6 mm.; in the frontal region, and below the eye, it is alittle broader. Posteriorly the opening is closed by a very well developed integumental fold resembling an ear-flap, which, with a breadth coequal with that of the true ear-flap, extends the entire length of the auricular opening, and both above and below indistinguishably merges into the ear-flap proper. Thus the entire aural aperture is surrounded by a continuous, free, and rather high dermal fold. The contour assumed by this posterior integumental fold is that given it by the form of the cranium; thus it is high on the right side, and comparatively as low on the left, where the osseous crest of the os sguamosum holds such an abnormally low position. 158 SHUFELDT. [Vor XVII. The nostrils are small and oblong; their height, which is hardly 3 mm., is greater than their width; they are subvertical in position, with their openings somewhat anteriorly directed. Posterior to the nostrils, the cere constitutes the swelled part, and this, superiorly, develops two tubercle-like elevations. The cranium, which is profoundly asymmetrical, is compara- tively large, with orbits of about medium size. The asymmetry is present upon both sides, but the left is the more abnormally so. In its structure generally it agrees, perhaps, in so far as the inland species are concerned, most nearly with the cranium of Syrnzum aluco, although it widely departs even from it. Its greatest vertical height is at a point posterior to the orbits. Longitudinally the superior aspect of the cranium presents for its entire length a feeble median furrow, which is best marked in the frontal region, between the supraorbital processes. A rather well marked cranio-facial hinge stands between the not very powerfully developed supe- rior mandible and the frontal bones; this mandibular portion is comparatively short, for, upon being measured from the frontalia, it will enter 2.6 times into the total length of the cranium, provided its horny theca is not taken into account. Posterior to the supraorbital processes the frontal region is rather broad; the area anterior to the processes rapidly nar- rows as we pass forwards, and it has quite concave borders. The asymmetry.— The bones that take part in the asym- metry of the cranium are principally the os sguamosum, and in a lesser degree the adjacent parts of the frontal, the parietal, and the alisphenoid.! The frontal bones are smoothly and very completely bounded off where they enter into the posterior peripheries of the orbits, 1 The internal configuration of these bones can only be examined with certainty in the very young. If the individual has arrived at maturity, even if the downy plumage (the first feathers, which are moulted shortly after the bird becomes full grown) is still worn, the sutures among the separate bones have already disap- peared. Although I have made every effort to obtain the young just taken from the nest, I have not succeeded in securing them, having only obtained a pair of indifferent specimens of nestlings, and in these obliteration of the sutures had already partly taken place. So perhaps the above description of the defining of the separate bones in certain instances can be corrected or supplemented. No. 1.] THE CRANIUM IN THE OWLS. 159 and have the appearance of being almost quite symmetrical. Thus, their orbital portions do not seem to offer any difference upon the two sides, as both descend about an equal distance upon either posterior orbital wall; on the other hand, the lat- eral portion on the right side, where it articulates with the anteriormost apex of the parietal bone, and the here abnor- mally developed and much uptilted crest of the os sguamosum, is more elevated than on the left side. Otherwise the differ- ence is very slight. The osseous crests on the os sguamosum, where the asym- metry is most evident, are, upon the whole, so abnormally large, deep, and conspicuously outstanding, that they, almost in their entirety, can be seen beyond the orbits, if the cranium be viewed from in front. As in the genus Aszo, they are not distinguished from any of the bones with which they articulate above by any distinct groove or depression, but enter into the uninterrupted lateral contour of the cranium, where it is seen from in front. Both sides are distorted, the left side being the more so. On the right side, the osseous crest is extended up- wards to a height quite coequal with that of the superior border of the orbit, but it abruptly terminates here, as it comes in con- tact with the frontal, at a considerable distance (7.2 mm.) pos- terior to the orbit, and in this manner crowding far backwards the apex of the parietal bone. In the middle the osseous crest is produced in such a way as to form an anterio-inferiorly directed and rounded process, which with its point impinges upon the hinder border of the orbital crest of the os alisphe- noides. The combined heights of the osseous crests upon this side are equal to 20 mm. On the left side the osseous crest is abnormally vertically compressed ; it commences at a point above, at about opposite the middle of the orbit, and close to the latter’s hinder border, thus being farther forward anteri- orly than it is upon the right side, as the crest is here sup- ported by the superior extremity of the orbital crest upon os alisphenoides. Here also, froma point a little below its middle, the crest is produced in a long, inferiorly directed process; but its apex is found as low down as the mandible, where, with a feeble, yet with an easily distinguished articulatory facet, it 160 SHUFELDT. [Vot. XVII. meets the jaw, as well as the os guadratum and the os jugale, at their point of articulation. It is in this way that the cra- nium itself comes in contact with the lower jaw, a phenomenon which is certainly without parallel in the class Aves, outside of this genus. Owing to the unusual development of this osseous crest, the fossa, in which the aural entrance is found, is of con- siderable width, particularly upon the right side. On the other hand, the entrance to the ear itself is normal upon both sides, and quite symmetrical; and, as the asymmetry is thus mainly confined to the external osseous crest and its neighboring struc- tures, while the os sguamosum, internally, is normally devel- oped, upon either side, it follows as a result that the inner walls of the brain casket are symmetrical, and the brain itself does not appear to offer anything anomalous in so far as its superficies are concerned. The parietal bone upon the left side, on account of the lowly situated osseous crest of the os sguamosum, is quite pointedly produced anteriorly, though it extends forwards quite to the hinder margin of the orbit ; on the right side, where the osse- ous crest is situated higher up and at the same time placed farther backwards, it is less pointed, though crowded farther to the rear, and as a consequence does not reach to the poste- rior border of the orbit. The alzsphenozd is, upon the right side, larger and posteriorly broader than it is upon the left side; in other respects the orbital crest does not present any asymmetry, that is, beyond the fact that its superior border is extended a little higher up on the right side than it is upon the left. The zuxterorbital septum is, anteriorly, quite thin and trans- lucent ; the os ethmotdes has a comparatively thick wall. The supraoccipital (squama occipitis) is pierced by a small supraoccipital foramen (diameter 34 mm.). The pterygotd bones are slender, being somewhat compressed from above downwards, thus causing their cultrate edges to turn obliquely outwards and downwards. The palatine bones are very broad; the pars plane upon the mesethmoid are quite short, and do not extend beyond the ex- ternal palatine borders, when the cranium is viewed upon its basal aspect. No. 1.] THE CRANIUM IN THE OWLS. 161 Vomer is present, but is very slender; in subadult individ- uals it is probably unossified (that is, Aadagtigt, or skin-like). The maxillo-palatines are, mesially, almost in contact upon their inferior side. [Conclusion of the translation. ] Opinions upon the Position of the Strigide in the System. Huxley, in his celebrated paper ‘‘On the Classification of Birds,” published in the Proceedings of the Zovlogical Society of London in 1867, says that his Aetomorphz is a division which is equivalent ‘to the ‘Raptores’ of Cuvier —an emi- nently natural assemblage, and yet one the members of which, as the preceding enumeration of their characters shows,! vary in most important particulars.” «They appear to me to fall naturally into four well-defined primary groups—the Strigid@, the Cathartide, the Gypetide, and the Gypogeranide. But this arrangement is so different from that ordinarily adopted that I shall proceed to justify it by enumerating the principal circumstances in which the members of the several divisions agree with one another and differ from the rest.” This is first followed by a fairly complete résumé of the osteological and other characters of the owls; but as many important skeletal strigine characters have, since that paper was published, been described by ornithotomists, I will com- plete Professor Huxley’s opinion by what he thought of the systematic position of the Caprimulgide, which he believed “come near Zvogon, and more remotely approach Podargus and the Owls”’ (p. 460). This is important, for as early as 1867 so keen an observer as Huxley saw the affinity between the goat-suckers and the owls. In his admirable article “Ornithology,” in the ninth edition of the Excyclopedia Britannica (Vol. XVIII, p. 47), Pro- fessor Newton says that “it has so long been the custom to 1It has not been thought necessary to give these characters here; they are surely not of a nature to convince one that a typical hawk, an American vulture, and an owl all belong to the same group; for example, Accipiter + Cathartes + Strix!—R. W. S. 162 SHUFELDT. [VoL. XVII. place the owls next to the diurnal birds of prey that any attempt to remove them from that position cannot fail to incur criticism. Yet when we disregard their carnivorous habits, and certain modifications which may possibly be thereby induced, we find almost nothing of value to indicate relationship be- tween them. That the S¢vzges stand quite independently of the Accipitres as above limited can hardly be doubted, and, while the Pszttaciz, or parrots, would on some grounds appear to be the nearest allies of the Accipztres, the nearest relations of the owls must be looked for in the multifarious group Pzcarze. Here we have the singular S¢eatornis, which, long confounded with the Caprimulgide, has at last been recognized as an inde- pendent form, and one cannot but think that it has branched off from a common ancestor with the owls.’’ But the same eminent authority, in the volume just quoted, under the article « Owl,” further says, on page 89, that “the owls form a very natural assemblage, and one about the limits of which no doubt has for a long time existed. Placed by nearly all systematists for many years as a family of the order Acczpztres (or whatever may have been the equivalent term used by the particular tax- onomers), there has been of late a disposition to regard them as forming a group of higher rank. On many accounts it is plain that they differ from the ordinary diurnal birds of prey more than the latter do among themselves; and, though in some respects owls have a superficial likeness to the goat- suckers, and a resemblance more deeply seated to the Guac- haro, even the last has not been made out to have any strong affinity to them.” ! «A good deal is therefore to be said for the opinion which would regard the owls as forming an independent order, or, at any rate, suborder, S¢viges. Whatever be the position assigned to the group, its subdivision has always been a fruitful matter of discussion, owing to the great resemblance obtaining among all its members, and the existence of safe characters for its division has only lately been at all generally recognized.” 1 Nevertheless, Professor Newton believes, at least, that Steatornis ‘has branched off from a common ancestor with the owls.” (Compare first quota- tion above.) —R. W. S. No. 1.] THE CRANIUM IN THE OWLS. 163 Upon consulting the plates and text of so distinguished an authority as Professor Max Fiirbringer, ‘“‘ Untersuchungen zur Morphologie und Systematik der Vogel,’ we are to note that there the Caprimulgi and Striges are considered as arising from a common ancestral stock, the suborder Coracizformes of the order CoORACORNITHES, and this last-named division is quite apart from the order PELARGONITHES, which contains - the Accipitres. In 1892 a no less careful examiner of the structure of birds than Prof. Hans Gadow published in the Proceedings of the Zoological Soctety of that year a very excellent article, in many respects, upon the “Classification of Birds,” and in the scheme set forth in that work Gadow placed the STrRIGEs in a group by themselves, standing between the parrots and the goat-suckers, and far removed from the Accipitres. Huxley, Newton, Fiirbringer, and Gadow must have especial weight attached to their opinions in the matter of the classification of Aves, for each and all of them carefully looked into and compared the anatomical structure of the members of this puzzling division of the Vertebrata. Many of the taxonomers of birds have not done this, and consequently are often guilty of classifying these forms upon such characters as strike their eye after a superficial examination of the general characters presented on the part of “series of museum skins.” In as yet unpublished MSS. the present writer has said : “Regarding the owls as a whole, they are to be considered as forming a group of nocturnal birds of markedly raptorial habits. Some of the species, however, are largely diurnal in their ways. They are not especially related to the Acczpztres, but are, on the other hand, remotely allied with the Caprimulgz. What we now know of the structure of such forms as Stea- tornts and Podargus sufficiently indicates this much.” This opinion is based upon an examination of the anatomy of the last two forms mentioned ; upon the osteology of all the species of North-American owls, Acczpztres, Caprimulgt, and a host of forms suspected of having alliance with these groups. In 1894 Mr. Hubert Lyman Clark published in the Pro- 164 SHUFELDT. ceedings of the United States National Museum (Vol. XVII, pp. 551-572 (many cuts)) a very able paper entitled “The Pterylography of Certain American Goatsuckers and Owls,” in which all the principal North-American forms were ex- amined. At the end of this memoir Mr. Clark said: ‘The conclusion, then, to which this study of their pterylography has brought me is that the Caprimulgi are related to Striges, and not very distantly either— probably a branch from the early part of the Strigine stem” (p. 572). My own opinions have been based upon a study of a// the characters of the groups we have under consideration; this, to a considerable extent, was the case likewise with Huxley; certainly so with Fiirbringer and Gadow, while Professor Newton gave the external characters and the skeleton the greatest weight. This being the case, the results arrived at by Mr. Clark very aptly fill in a gap that long stood greatly in need of the very kind of treatment he has bestowed upon it. As to what relations may exist between the owls and the parrots, I am, just now, not prepared to give a decided opinion; certain it is, however, that we have both “owl- parrots” (S¢viugops) and parrots in Australia that are suffi- ciently “rapacious” to make good enough use of their claws and hooked beaks to prey upon living sheep, and that display quite as much taste for the habit as a Budo does when he kills and devours a hare. —R. W. S. 166 SHUFELDT. EXPLANATION OF PLATE XV. (All the figures of the plates are by Professor Collett.) Fic. 1. Skull of Surnia funerea; anterior aspect, with mandible attached; natural size. Fic. 2. Skull of Surnia funerea ; left lateral aspect, with mandible attached ; natural size. Fic. 3. Head of Surniza funerea ; feathers removed and showing ear-opening; - natural size. Fic. 4. Skull of Glaucidium passerinum ; anterior aspect, with mandible attached ; natural size. Fic. 5. Skull of Glaucidium passerinum ; \eft lateral aspect, with mandible attached; natural size. Fic. 6. Head of Glaucidium passerinum ; feathers removed and showing ear- opening; natural size. Fic. 7. Skull of Aszo accipitrinus ; anterior aspect, with mandible attached ; natural size. Fic. 8. Skull of Aszo accipfitrinus ; superior aspect, with mandible attached; natural size. Journal of Morphology. Vol. XVII PEXY. B Meisel, hth,Boston ie ru) vat 7 ” + 168 SHUFELDT. EXPLANATION OF PLATE XVI. Fic. 9. Skull of Asio accipitrinus ; right lateral aspect, with mandible attached ; natural size. Fic. 10. Head of Asio accipfitrinus ; left lateral view, with feathers removed and showing ear-opening; natural size. Fic. 11. Head of Asio accipitrinus ; right lateral view, with feathers removed and showing ear-opening; natural size. Fic. 12. Skull of Asio otus; left lateral aspect, with mandibie attached; natural size. Journal of Morphology. Vol. XVij PLXVI ‘ EIEN ti } ay aN 170 FIG. 13. natural size. FIG. 14. natural size. FIG. 15. natural size. Fic. 16. natural size, SHUFELDT. EXPLANATION OF PLATE XVII. Skull of Syrnium aluco ; left lateral aspect, with mandible attached ; Skull of Syrnium aluco; anterior aspect, with mandible attached; Skull of Syrnium uralense ; anterior aspect, with mandible attached : Skull of Syrnium uralense ; left lateral aspect, with mandible attached; Journal of Morphology. Vol. XVII Jae OIE > vo ie fl! 172 SHUFELDT. EXPLANATION OF PLATE XVIII. Fic. 17. Head of Syrnium aluco; right lateral view, with feathers removed and showing ear-opening ; natural size. Fic. 18. Head of Syrnium aluco; \eft lateral view, with feathers removed and showing ear-opening; natural size. Fic. 19. Skull of Syrnium aluco; basal aspect, with mandible attacned ; natural size. Fic. 20. Skull of Syrnium aluco; superior aspect, with mandible attached ; natural size. PLXVI, Journal of Morphology. Vol. XVII B. Meisel, lith,Boston 174 SHUFELDT. EXPLANATION OF PLATE XIX. Fic. 21. Skull of Myctala tengmalmi ; anterior aspect, with mandible attached ; natural size. Fic. 22. Skull of Vyctala tengmalmi ; posterior aspect, with mandible attached; natural size. Fic. 23. Skull of Myctala tengmalmi; right lateral aspect, with mandible attached; natural size. Fic. 24. Skull of Myctala tengmalmi; \eft lateral aspect, with mandible attached; natural size. Fic. 25. Head of Myctala tengmalmi; right lateral aspect, with feathers removed and showing ear-opening; natural size. Fic. 26. Head of Wyctala tengmalmi; \eft lateral aspect, with feathers removed and showing ear-opening; natural size. Fic. 27. Skull of Syrnium lapponicum ; \eft lateral view, with mandible attached; natural size. Pl. X1X. gy. Vol. XVI holo Journal of Morp 5, Meisel, lith Boston . oF ' — > = : : ' ' . i I . rs ' a 4 ‘ 4 Fb, i 176 SHUFELDT. ° EXPLANATION OF PLATE XxX. Fic. 28. Head of Syrnium lapponicum ; left lateral aspect, with feathers removed and showing ear-opening; natural size. Fic. 29. Skull of Syrnium lapponicum ; right lateral aspect, with mandible attached ; natural size. Fic. 30. Head of Syrnium lapponicum ; right lateral aspect, with feathers removed and showing ear-opening; natural size. Journal of Morphology. Zi d. B Meisel, lith, Boston Volume XVII, June, IQOL. Vo. LN} JOURNAL OF MOK EHO Ogi NOTES ON AEOLOSOMA TENEBRARUM. EDITH M. BRACE. Acolosoma tenebrarum, a fresh-water oligochaete belonging to the Aphaneura, has been supposed to hold a unique posi- tion among annelids, having been described as having a brain but no ventral nerve cord. Vejdovsky, Maggi, and Beddard have given the more de- tailed accounts of its structure. Vejdovsky! found a few cells supposed to represent a rudimentary nerve cord which was not connected with the bilobed brain: “ Bei A. tenebrarum treten auf der Bauchseite zerstreute Elemente hervor, die auf eine nervose Natur hinweisen.’”’ And again: “Man erkennt in der Centrallinie der Bauchseite, eine kurze Strecke hinter der Pharyngealregion, eigenthiimliche, aber sehr undeutliche Zellen- und Fasserstrange, die jedoch mit dem Gehirnganglion nicht zusammenhangen.”’ From the plates it is impossible to tell just what cells are referred to, but as they were found in the median line, they could not have been a part of the ventral cord. Maggi” has described a brain, ventral cord, and lateral nerves for Aeolosoma: ‘Un cordone schiacciato che si estende lungo 1 Vejdovsky, F. System und Morphologie der Oligochaeta. 1884. 2 Maggi, L. Intorno al genere Aeolosoma. 186s. 177 178 BRACE. [Vou. XVII. tutto la linea mediana ventrale dell’ animale mandando laterala- mente degli esili fili nervosi, ed un ganglio cefalico consti- tuiscono per quel che potei scogere, il sistema nervoso degli Aeolosoma.” This description has not generally been credited. He gives no illustrations of the nervous system, and his drawing showing the mouth at the end of the prostomium, with the space inside the prostomium designated as the buccal cavity, leaves no place for a brain and is incorrect, as well as the statement that the nerve cord extends along the median ventral line. Beddard! says of A. tenebrarum: “This species alone shows any traces of a ventral cord, which is very short and is not connected with the brain.” A further study of the subject was undertaken in the Zo6o- logical Laboratory of the University of Chicago, at the sug- gestion of Professor C. O. Whitman, to whom I am indebted for the supervision of my work. Material for study was found among the water plants in the park ponds of Chicago, where it was especially abundant around the water hyacinth and Vectorza regia. The worm is not an active swimmer, but prefers to lie among the algae or to crawl between the meshes of a decaying leaf. It is white and semi-transparent, and the integument is studded with innumerable green oil drops contained in gland cells which have their large nuclei flattened against the cell wall, similar to the gland cells of the Turbellaria. A delicate chiti- nous covering may be seen after treatment with reagents. The worms feed upon algae or bits of decayed leaves and have a tendency to collect on the sunny side of the aquarium. They vary in length from 3 to 10 mm. A number of worms will frequently get together, twist them- selves into a ball, and remain so fora long time. It has been suggested that this was connected with conjugation, but that is improbable; they are presumably feeding upon each other, as one worm is usually found partly eaten, if the ball is pulled apart. They have great powers of regeneration; in one case, where the head had been eaten away to the first pair of setae, a new head was regenerated in about three days. 1 Beddard, F. E. A Monograph of the Order Oligochaeta. 1895. No.2.] MWOTES ON AEOLOSOMA TENEBRARUM. 179 The head segment, which is broader than the following segments, is separated from them by a constriction, and seen from above, it appears to have a ciliated pit on each side like those of the Turbellaria. The mouth is on the ventral side and is overhung by the prostomium, which is ciliated on its lower surface, and serves as a tactile organ. There is no proboscis. Intersegmental septa were not found, but the segmentation is defined by the nephridia and the setae. Each segment has one pair of nephridia and four bundles of setae, placed dorso- and ventro-laterally. There is also a segmental arrangement of single, nucleated muscle fibers which extend from the ali- mentary canal to the body wall between the setae sacs. The alimentary canal comprises a circular mouth opening into a bell-shaped pharynx, followed by a narrow oesophagus, which extends through two segments and leads to a broad stomach with glandular walls, which extends through the sixth segment where it narrows into a straight intestine. As the worms are transparent the movements of the cilia lining the ali- mentary canal may be seen in the living specimen. The muscular system is comparatively simple. There is one layer of longitudinal and one layer of circular muscle fibers just beneath the epidermal wall, and single nucleated fibers are con- nected with the setae and hold the various organs in place. These single nucleated fibers are especially numerous in the head and resemble the muscle plates of the Turbellaria. The worms were under observation from October until July, and during that time they were constantly reproducing by fis- sion, with sometimes as many as three zodids developing at once. Back of the seventh setigerous segment there is a fis- sion zone in which all the tissues of the epidermal wall are greatly thickened, especially on the ventral side, where they nearly obliterate the body cavity. The new brain arises as a dorsal thickening of the epidermis. No sexual reproduction was observed. Methods. — At the slightest irritation the worms will coil in a circle, throw off the contents of the gland cells, and con- tract so violently that the tissues are injured for study. To 180 BRACE. (Vou. XVII. secure good specimens for sectioning they were mounted ona slide and held in place by a cover-glass that pressed on them slightly. They were then placed on ice for a few moments until chilled and unable to contract any portion of the body, when they were treated with the fixing fluid. The cold also prevented abnormal activity of the glands, so that very perfect preparations were obtained, although the worms will go to. pieces if left on the ice too long. The fixing fluid after the second formula of vom Rath (picric + acetic + osmic + platinum-chloride) was found most effect- ive in demonstrating the nervous system. Specimens were left in this for fifteen minutes, washed in alcohol, and placed in a 20 per cent solution of tannin in acetic acid for periods of time varying from twenty-four hours to four days, or else they were stained in section with safranin or iron-haematoxylin after vom Rath. Paraffin was used for imbedding, and sections were cut from 3-20 thick. Sections from 10-15 uw thick were found most favorable for study. Nervous System. — The brain lies in front of the mouth in close contact with, and partly imbedded in, the epidermal wall (Pl. XXI, Figs. 1, 6-8), the lower part projecting more or less into the cavity of the prostomium. Its ventral and lateral sur- face, so far as free from the epidermis, is covered by a delicate nucleated membrane which may be seen in section. It hasa slightly bilobed appearance, as seen from above, each half having a rounded anterior margin and a large posterior lobe, the latter composed entirely of nerve cells (Pl. XXI, Figs. 2, 3). Closely packed nerve cells with large granular nuclei cover the whole dorsal surface, and are from three to four cells deep in the anterior and posterior lobes, but only one layer deep in the middle region where the anterior lobes meet (Pl. XXI, Figs. $,o00): A pair of nerves composed of fibers partly from the brain and partly from the oesophageal commissure, runs forward from the brain into the prostomium, and another pair runs back from the angle between the posterior lobes and the com- missures (Pl: XI, Pigs. 1512595520) 9): No.2.) MOTES ON AEOLOSOMA TENEBRARUM. 181 Commissure. — Immediately after leaving the brain the oeso- phageal commissure passes into an accessory ganglion, from which a nerve runs forward into the prostomium (Pl. XXI, Fig. 1). It then passes downward and backward, in close con- nection with the epidermal wall, to the ventral side, where it expands into a second ganglion before passing into the ventral cord (Pl. XXI, Fig. 1). The fibers of the commissure form a broad band which is clearly distinguishable, but it is often difficult to determine whether the cells along its course belong to it or to the epidermis. Ventral Cord. —The two parts of the ventral cord are sepa- rated by about one-fifth of the diameter of the body and com- municate with each other by fibrous commissures, forming the ladder type of nervous system (Pl. XXI, Figs. 1, 12). There is one pair of ganglia in each segment, and each ganglion is deeply bilobed, the anterior lobe being somewhat smaller, while the posterior lobe extends out farther in the body wall. The fibrous portion forms the greater part of the ganglion, and is covered by cells one layer deep (Pl. XXI, Fig. 11). Inthe posterior segments the ganglia are crowded together more closely than in the anterior segments (Pl. XXI, Fig. 1). Lateral Nerves. — Four distinct lateral nerves are given off from each ganglion, two from the anterior and two from the posterior half (Pl. XXI, Figs. 1, 11). This whole system of brain, ventral nerve cord, commissures, and nerves is connected throughout with the epidermal wall, no portion of it being entirely free in the body cavity. The cells of the ventral ganglia, as well as those of the brain, are often so closely connected with the epidermis that it is hard to find the boundary line between them. The nuclei of the gan- glion cells are of about the same size as those of the epidermis, but stain a little more deeply. Ciltated Pits.— Vejdovsky! states that in Aeolosoma we find the only instance of an oligochaete possessing a pair of lateral ciliated pits, and he compares them with the ciliated pits of the Turbellaria. From the dorsal side the appearance is very similar to these organs in the Turbellaria, but frontal 1 Vejdovsky, F. Thierische Organismen der Brunnenwisser von Prag. 1882. 182 BRACE. [Vou. XVII. sections of the ventral side show that they are not pits at all, but the terminations of deep ciliated grooves which curve for- ward and outward from the mouth to the edge of the pro- stomium (Pl. XXI, Fig. 13). The mouth is circular, bordered posteriorly and laterally with a thick swollen lip, which may be greatly extended, and which is continued as the posterior wall of the ciliated furrows. The cilia of the grooves, and those around the mouth, are excep- tionally long. Sense organs are as numerous along either side of the furrows as on the prostomium. Vejdovsky describes a nerve connecting the lateral pits with the brain. I find muscle fibers here, but no nerve, and from the nature of the structure should not expect to find one. Sense Organs.— There are many large pear-shaped cells, that have the appearance of sensory cells, lying in all parts of the prostomium and disposed through the body segments (Pl. XXI, Fig. 14). The cytoplasm of these cells is finely gran- ular and deep-staining, the nucleus is of medium size, coarsely granular, and usually eccentric, taking its position at the base of the cell. Between the nucleus and the opposite end of the cell there is a large, sharply outlined, clear space containing a refractive body with peculiar granulations at its periphery (Fig. 14) which may represent an otolith. These cells are sometimes isolated, but are often collected into small groups (Fig. 15), as seen to best advantage in the prostomium. They suggest sense organs of some kind. They have no pigment. At the anterior end of the prostomium there is a group of about fifteen of these large compound organs, crowded together so closely that their sides are somewhat flattened against each other (Fig. 16). Back of these there are smaller compound sense organs, some distance apart, arranged in rows across the ventral surface of the prostomium, and there are large sense organs along both sides of the ciliated furrows leading to the mouth (Fig. 16). The smaller compound sense organs are also found on the ventral side of the segments back of the mouth. All of these sense organs lie immediately under the epidermis, so that they project slightly into the body cavity. Aeolosoma undoubtedly possesses the essential annelidan No. 2.] NOTES ON AEOLOSOMA TENEBRARUM. 183 characteristics, although Vejdovsky favored classifying it with the Turbellaria on account of the similarities which he found between the ciliated pits, muscle plates, and gland cells of these forms, together with the structure of the brain and the sup- posed lack of a ventral cord. The course of the large nerves running back from the brain has not yet been traced for an annelid; they present an anom- alous feature which is most interesting from its suggesting a possible transitional form of nervous system between unseg- mented and segmented worms. The position of the brain in the first segment, the continuity of the entire nervous system with the epidermis, and the wide separation of the halves of the ventral cord are primitive characteristics which would be consistent with such a form. REFERENCE LETTERS. ag. accessory ganglion. mo. membrane lining the body-cavity @ -brain: and covering the free, lower c. connecting commissures of the surface of the brain. ventral nerve cord. mf. tauscle fibers attached to the cl. cluster of large sense organs in brain and connecting it with the the end of the prostomium. epidermis of the ventral side. d. second ganglion of the oesopha- %. nucleus. geal commissure. 7.1.3 first, second, and third pairs of ep. epidermal cells. cephalic nerves. f lateral ciliated furrows leading to | zm. nuclei of the lining membrane. the mouth. o. refractive body. g. gland cells. oc. oesophageal commissure. /. lip bordering the mouth and the . posterior ganglionic lobes. ciliated furrows. v. vesicle containing a refractive 7x. lateral nerves. body. m. mouth. ve. ventral nerve cord. 184 BRACE. EXPLANATION OF PLATE XXI. Fic. 1. Frontal view of the central nervous system, reconstructed from sec- tions. (X 210.) Fic. 2. Ventral view of the brain. (x 1200.) , Fic. 3. Dorsal view of the brain, showing its bilobed form. (x 1200.) Fic. 4. Frontal section near the middle of the brain, showing the first pair of nerves. (X 800.) Fic. 5. Frontal section next above Fig. 4. (x 800.) Fic. 6. Sagittal section of the brain in the plane of the anterior nerve and the posterior lobe. (x 800.) Fic. 7. Sagittal section of the brain a little nearer the middle than Fig. 6. ( x 800.) Fic. 8. Sagittal section near the middle of the brain, showing a single layer of cells on the dorsal side. (x 800.) Fic. 9. Oblique section of the brain, showing the posterior lobe and the roots of the first and second cephalic nerves. (x 800.) Fic. 10. Cross-section of the brain in the plane of the commissure. (x 800.) Fic. 11. Frontal section through a segment of the ventral nerve cord, showing the roots of the lateral nerves and of the connecting commissures. (X 1200.) Fic. 12. Cross-section of the ventral nerve cord in the thoracic region, show- ing the ganglia connected by a commissure. (x 800.) Fic. 13. Drawing showing the mouth with the furrows leading to it, and the prostomium, ciliated on the ventral side. (x 1200.) Fic. 14. Pear-shaped sensory cell, with vesicle containing a refractive body. (X 1200.) Fic. 15. Sense organs composed of several cells similar to those of Fig. 14. (X 1200.) Fic. 16. Partial diagram showing the position of the compound sense organs on the ventral surface of the prostomium. (x 1200.) Saud of Morphology. Vol. XVI. Ci “U )ef : is : 7 Tih Werner @Weter, Franktore if, MOK PHOLOGY ‘OF THE MY XINOIMDET. I SKELETON AND MUSCULATURE. HOWARD AYERS anp C. M. JACKSON. CONTENTS. PAGE TST OND ODEO Nf esac aie ctivece es daa enncc homes eucbcnesienuch caitonsbuoe OAS cae hs Le ma ee ee 185 Alera RoeE: MONG (UIN RGN RUA TS) | oo. 2 noc as5.t nc collee cave asuzsonec-Oohcsueceeeseee ce ate eeene one 189 a. Endoskeleton (general) Intermuscular Septa...............0.c2.ceccecssseeeeeeneesseeeees 190 a. Notochord, Structure, and Position, Sheaths, Neural Canal.............. 190 B. Skeleton of Head Region (skull as a whole)..................csssssenesssssessees 193 neem branousy © ramus se .02e Ss ae ee ae eee ee 194 2. Parachordals, Auditory Capsules, and Trabeculae................000--+- 194 BrEiypophysial aelaterands (Cam ally esse ence seee nee ase ee ee 196 AaOltactonye Capsule ance Nasal wien ss eesst ee nena 196 5. Cornual and Subnasal Cartilages ......... beaolie ia eee 200 Owleabialyand Mentaculars Cartila ges: seer cebe ee ene ence 201 7basalyPlaterand, Mandibular Cartilacesii sss 202 8. Palato-Pterygoid and Epi-Hyoid Arches .......................- areas e207, © Anterior branchials and) Velar)@antilagesy sss sce ene 209 HOw GillPancdiMiuscles Gartilag es. see2 ice. ceecs eee eer a 212 py sm AUG al C1 OM bee ecco oe even decet dees casves coe eee ee 214 1. Median Dorsal and Ventral Bars, Neural Ring.............s.ssccee-0e---- 215 PB RAY Se hea cases gst: ech cnsedencna ionnensictnet cotsctsnst 171 43- mies set a from the coast of Chili, 10 gills, 11 | 1 (Lacépéde), 12|42, 13 paeneeee from the ae of California, 11 to 13 gills, 3 | 8, In the California series examined by Dr. Ayers the dental formulae were as follows: In 22 individuals with 11 gills, 10 sh 10 | _9 10]10 10/10 pay ee) alt) |) aL 1 1 10 lio et TOE || eee 1 9 [0 1 KOM SO? 1 ro | One i i i) jf ata JE ae) plat ta) dat |) gia aba eat 1 9 oe 1 a ete 3 +o | to 1 rt law 5 154d 1 4 40 IEPA Wa Wey || ab eA 1 3 esas 2 relat No. 2.] MORPHOLOGY OF THE MYXINOIDET. 219 In 62 individuals with 12 gills the following dental formulae occurred: 1 8/18, 18/8, 8 2/10, 1/49, 1/19, 2121/2 0110? 9) 192 L4$]8 148i 10 WA 4 4g] ae 6 BLES T ARLES, Lett, LARA LAL 1 ALAR 10 HIE 8 44 4b L abt 149143. On combining the dental formulae of the 11-gilled and 12- gilled variations, the following numbers were found to obtain in the 86 individuals whose dental formula was carefully examined on both sides of the dental plate. NuMBER oF INDI- TAGLAR. NuMBER CH Mor Thane Renee VIDUALS. VIDUALS. 1 318 2 [44 8 sit? 1 rakes 1 fol ? 81th 1 oot 1 tg. [3h 3 18 1 th | 1 1818 13 14 2 18 | 1 1/4 . Wty 8 5/44 8 a8 1 HLH 4 ak 1 5148 7 +8148 1 1B | : aoe 3 elke Total number 86 In the series of 162 specimens from Monterey Bay examined by Mr. Jackson, the following dental formulae were observed: Branchial formula, 1o-10:—1 g| 2. i 1) OT A | ao) 10 |10 a) || EL Branchial formula, 11-11: —1 10/10, 11 12|19, 4 19/19, play (gl Ds 20 aly) aeae At) |) Lo) BLO cals WAL |) SLL Lit ites 8 the 4 dbl 4h 2 thle 1 Plat, 1 aa, ea eg (ae, JLal |} aL) LAL) ala Ua) Let Ye | Ee JUL |) 2s 275150 8 45/40 T4ablth 1 ab] 1 bh 1 41 226 AVERS AND JACKSON. [VoL. XVII. Branchial formula, 12-11:—3 1 |4f, 3 42|13, 3 18) 108, 1 i0)ta, 219/10, 2 14/49 8 11 |1it. Total, 17. Branchial formula, 12-12:—1 2/8, 1 3|,%, 2 2|43, 16 30/18, 4 IP|4G, 1 ARH LABIAE 8 APIS 8 ALLA, 28 49/48, 8 14h 4 dh|4h 2 4b] 1 gldb 1 48) M 23g |4e, 244 be 18 44/4 2 Ag BE 1 ES 1 44H 1 12| 12. Total, 88 Branchial formula, 12-13:—1 1] 1%. Branchial formula, 13-12 :—1 12/48, 1 14)14 Branchial formula, 13-13:—1 1°|19, 1 42/418, 1 10\16 Total, 3. The following table is a summary of all the variations found in the 162 specimens observed. whee eo Lis DENTAL FORMULA. SIUM EE GE DING E DENTAL FORMULA. VIDUALS. VIDUALS. 2 alg 6 x | 4h 1 $|70 - 45 | 4 2 he 2 48 [3 1 3 |e 1 04h 31 1 |p 24 ab lt 10 ap | 44 9 1148 4 ae 9 1814 2 tolis 1 45 | 4? 6 wag 1 15134 4 a 1 1b )F 1 ag | AL 1 16148 1 1 [gh 1 tlt 1 1A 1 +148 6 1 4 1 12 |g 31 +8148 Total number 162 No. 2.] MORPHOLOGY OF THE MYXINOIDEI. 221 From a comparison of the above dental formulae, including in all 248 specimens, we conclude: (1) That there is an exceedingly great variation in the num- ber of the teeth, even more striking than in the case of the gills. Thus these two characters (the number of teeth and gills), the only two “constant” characters which Johannes Miller could find upon which to base his classification, are both proven to be extremely variable. (2) In a large number of cases the two sides of the dental plate are not symmetrical with regard to the number of teeth. It is to be feared that the dental formulae given in systematic accounts of Bdellostoma are, in many cases, based upon counts of one side only of the dental plate. (3) There is no constant relation between the number of teeth and the number of gills. If there is any difference at all worthy of note, the individuals with the larger number of gills have a smaller proportion of teeth than might be expected. (4) There is no constant relation between the number of teeth and the size or sex of the individual. The size and sex, though not given in the above tables, were noted in every case. While we should naturally expect that the larger individuals would have a larger number of teeth, this is usually not the case. Ina 23-inch specimen, for example, which is considerably above the average size, the dental formula was 3 | 1). (5) The outer rows of teeth have in a majority of cases a greater number of teeth than the inner. In 312 cases the teeth of the outer row were more numerous than those of the corresponding inner row. In 178 cases they were equal. In only 6 cases had the inner rows a greater number - teeth. Bat, The dental formulae eon oftenest are: 1,°| 4° (45), & (88), 44/44 (82), 44]48 (22). It is ae that we eaniot ek HY ‘ony one “4 @eypiedl” or predominant formula. More than half the rows of teeth number 10 however, and in nearly half the cases the corresponding outer and inner row each contains 10 teeth. The number g is given next in fre- quency, but occurs less than half as often as 10. More than 95% of the rows include either 9, 10, or 11 teeth. The Chilian specimens seem to average a larger number of 222 AYERS AND JACKSON. [VoL. XVII. teeth, for Girard counted in his type specimens with 14 gills 12/12, while Putnam found +3 |13 or 42] 42 in the material he studied from Talcahuano Bay (Hassler expedition), reported as having 10 gills. Lacépéde’s example from Chili had the very unusual dental formula of 14-| 41. A critical histological study of the dental structures of Bdellostoma is reserved for a separate paper. But it may be mentioned that the hollow bases of the corneous teeth rest upon soft dental papillae, which are fused together below into a bar extending the entire length of the row of teeth. These papillae are epidermal in origin, and the teeth are simply corni- fied sheaths of the epidermal elevations upon the dental plate. They are easily sectioned when imbedded in celloidin, and show no traces of dentine, enamel, bone, or calcareous matter of any kind. March, 1808. (To be continued.) Nov2.] MORPHOLOGY OF THE MYXINOIDEL. 223 SYNONYMOUS TERMS FOR SKELETAL PARTS. AYERS AND JACKSON. Notochord ; Cellular sheath of same . Fibrous core Notochordal sheath Skeletogenous layer, elastica externa Neural tube . Auditory capsule Parachordals Trabeculae Hypophysial plate Subnasal cartilage . Transverse labial cartilage . Lateral labial cartilage Nasal tube Olfactory capsule . Cranium . Ale Tentacular cartilages . Dental plate . Teeth . Anterior segment of basal plate . Middle segment of basal plate Posterior segment of basal plate . Palatine bars Cornual cartilages . Pterygo-quadrate . Hyoid arch Superior lateral cartilage Inferior lateral cartilage. First branchialarch . . . . Second branchial bar. External lateral bar Internal lateral bar Suprapharyngeal plate JOHANNES MULLER. Gallertsaule. Innere Schicht. Faser-Faden. Innere Scheide der Gallertsaule. Aeussere Scheide der Gallertsaule. Riickenmarksrohr. Gehorkapsel. Knocherne Basis cranii. Fliigelfortsatze derselben. Gaumenplatte. Knocherne Stiitze der Schnautze. Innerknorpel. Knorpel-Fortsatz am vordern Ende des Zungenbeins. Nasenrohr. Nasenkapsel. Gehirnkapsel. Mundknorpel. Zunge. Zahne. Vordere Reihe der Zungenbein-Kno- chenstiicke. Hintere Reihe der Zungenbein-Kno- chenstiicke. Knorpeliger Kiel des Zungenbeins. Gaumenleisten. Knorpel-Fortsatz am vorderen Ende der Gaumenleiste. Unterer Fortsatz der Gaumenleiste. Verbindung der Fortsatze mit der Gehorkapsel. Oberer Fortsatz des Schlundkorbes. Unterer Fortsatz des Schlundkorbes. Grosses Horn des Zungenbeins. Kleines Horn des Zungenbeins. Hauptsttick des Schlundsegels. Mittel-Riemen des Schlundsegels. (In part-) Aufsteigende Fortsatze des Mittelriemens. 224 AYERS AND JACKSON. EXPLANATION OF PLATE XXII. Fic. 1. A cross-section of the notochord, spinal cord, and sheaths of Bdellostoma a short distance behind the cranial region (x 10, camera lucida outlines). Fic. 2. A cross-section of the notochord, spinal cord, and sheaths of Bdellostoma in the posterior gill region (xX 10, camera lucida outlines). Fic. 3. Section of the notochord and its envelope. Fic. 4. A cross-section of the cranium of Bdellostoma through the region of the auditory capsules (Xx 20, camera lucida outlines). Fic. 5. Dorsal view of the skull of Bdellostoma (x 2). Fic. 6. The skull and the skeleton of the pharyngeal region of Bdellostoma, lateral view. The roof of the spinal canal, the oesophagus, the gills and gill passages, and the retractor mandibuli muscle are outlined with dotted lines (x 2). A. = auditory capsule. mp. = internal process of lateral a. = anterior connecting process. labial cartilage. B. = anterior segment of the basal A# = notochord. plate. 2. = nucleus. B’ =middle segment of the basal #.s. = notochordal sheath. plate. 4V. = subnasal bar. BY” = posterior segment of the basal .7. = nasal tube. plate. Oes. = oesophagus. é. = superior lateral cartilage. oes.c. = oesophago-cutaneous duct. b! = inferior lateral cartilage. O.C. = olfactory capsule. ér4 = Ist “branchial” arch. P.Q. = pterygo-quadrate. ér.. = 2d “branchial” arch. fi. = palatine bar. By: — prem pc. = parachordal cartilage. Cr. = cranium. S. = supra-pharyngeal plate. ¢.¢. = cornual cartilages. sc. = neural tube. ¢.s. = superior chondroidal bar. s.6. = basal process. ¢.. = inferior chondroidal bar. sk. = Skeletogenous layer. D. = dental plate. Sh.y = internal layer of notochordal d.t. |= median dorsal tooth. sheath. éx. = external cellular layer. Sh.g = middle layer of notochordal F. = “fatty” tissue of the neural sheath. tube. Sh. = external layer of notochordal #’ =similar layer within the cra- sheath. nium. Sf. = spinal cord. Fc. = fibrous core. 24, t.2, 43, 4.4 = Ist, 2d, 3d, 4th tentac- f.s.._ = fascia superficialis interna. ular cartilages. gb. = gill bar. Zr. = main bar of the trabecula. Hy. =hyoidarch * tr. = anterior horn of the same. fff. = hypophysial plate. Z = tendon of retractor mandibuli t.m.s. = intermuscular septum. muscle. Z.c. = lateral labial cartilage. ve. = vacuole. Z.. = lateral (ethmoidal) plate. V. = external lateral velar bar. m.j.e. = membrana limitans externa. V’ = internal lateral velar bar. m.d.s. = median dorsal septum. I, 2, 3, 4 = fenestrae of skull. m. = median connecting process. AVI. Vol ogy. 1 . es ren Ce ee Winter, Frankcore Oe bith Werner & 226 AYERS AND JACKSON. EXPLANATION OF PLATE XXIII. Fic. 7. A dorsal view of the skull of Bdellostoma, cranium, olfactory capsule and nasal tube removed (X 23). Fic. 8. The basal plate of Bdellostoma, ventral view (x 1). Fic. 9. A dorsal view of the basal plate of Bdellostoma (x 1). Dorsal view of the teeth and the dental plate of Bdellostoma (x 2). The dental plate of Bdellostoma, ventral view ( x 2). A gill bar of Bdellostoma, stretched out (X 8). The cartilage of the oesophago-cutaneous duct of Bdellostoma (x 4). The skeleton of the posterior region of Bdellostoma (x 1). A cross-section of the tail of Bdellostoma, taken just in front of 7, Dorsal and ventral portion of section not shown (xX Io). FIG. 10. Fic. 11. FIG. 12. FIG. 13. FIG. 14. FIG. 15. Fig. 14. A.i. = internal bars of anterior seg- ment. A.c. = external bars of anterior seg- ment. a.a. = lateral dental plate. av. = Cloacal cartilage. a.6. = anterior transverse velar bar. bv. = blood vessel. ¢.m. = palatine commissure. é. = process of median ventral cartilage. cm. = connective tissue. D.m. = dermal muscle layer. D.#. = dorsal fin. é: = posterior external process of lateral plate. ex.g.p.= external gill passage. Vi = auditory foramen. je. = tin-tay. £- = dorsal tendon groove. h. = superior process of oesophago- cutaneous cartilage. posterior internal process of lateral plate. anterior process of hypophysial plate. median dorsal bar. median ventral bar. median cartilage bar. median piece of dental plate. myotome. the oesophago-cutaneous bar. posterior transverse velar bar. posterior arch of dental plate. anterior connecting process of lateral plate. sheath of fin-ray. epidermis. transverse labial cartilage. anterior process of trabeculae. ventral fin. posterior connecting process of lateral plate. Journal. of Morphology. Vol.XVU. ‘Lith Werner RWinter, Frankfort 7 18 Ill. IV. GONTENTS OF V@EUMES Sy ir No. 1. — September, 1900. GusTAV EISEN, PH.D. The Spermatogenests of Batrachoseps . R. We SHUFELDT, M.D: Professor Collett on the Morphology of the Cranium and the Auricular Openings in the North-European Spectes Oe the ii Strigide No. 2. — June, rgor. Epity M. Brace. Notes on Acolosoma Tenebrarum Howarp AYERS AND C. M. Jackson. Morphology of the Myxinotdet. TI. Skeleton and Musculature FRANK R. LILLIE. The Organization of the Egg of Unio, based on a Study of tts Maturation, Fertilization, and Cleavage . HELEN DEAN KING. The Maturation and Fertilization a the | of Bufo Lentiginosus PAGES I-117 119-176 177-184 185-226 227-292 293-350 iv i, Ti IV. CONTENTS. No. 3. — July, Igo. PAGES W. S. NICKERSON. On Loxosoma Davenporti (Sp. Nov.) . . . 351-380 MARGARET LEwis NICKERSON. Sensory and Glandular Epidermal Organs in Phascolosoma Gouldit. . . . . . 381-398 Aaron L. TREADWELL. The Cytogeny of Podarke Obscura Verrill . 399-486 R. W. SHUFELDT, M.D. On the Osteology of the Pigeons (Columba). 487-514 KATHARINE Foot AND ELLA CHURCH STROBELL. Photographs of the ee o es Fretatan IE 6658 i 2 eo (eS kee eee THE ORGANIZATION OF THE EGG OF UNIO, BASED ON A STUDY OF ITS MATURATION, FERTILIZATION, AND CLEAVAGE. FRANK R. LILLIE. TABLE OF CONTENTS. PAGE TIN'TRODUCTION cccccsccccccssnccecccee soecce cence ene cececcensnocnn=snnnmerenennannnedacon@anesencnmenmaneconanssocoGiocs 227 J. THE BEHAVIOR OF THE SPERMATOZOON IN THE EGG UP TO THE TIME OF EXTRUSION OF THE SECOND POLAR GLOBULE........ 229 r. The Sperm-Nucleus ........-.-.---------2cscscvsseneccccssensenenssneeneerenncnceasertansennasss 229 2. The Sperm-Aster and Amphiaster: Origin and Disappearance.... 231 @. Observations .........-----..-cc2-c2cccceceee co ceeeecseneeeececeneceeemeneanenessscnnaneneners 231 B. Weiterature —.o222---ccccc.nccsenscceeeceeeseccnc sererdeenseecbaeanernenennecnrrssencentnanscnc 233 II. THE MATURATION OF THE EGG ..........22-.---------------ceccececesecercences ereeneneneanane 235 1. The Chromosomes ....... SF ok ee es ee ee ssdpeeesesteeveeacs 235 2. Achromatic Structures.........-..--2.-2-c-csscecesees cee cneeeneeectne teeeneeneenmenennc neces 236 III. GrowTuH, MIGRATION, AND UNION OF THE GERM-NUCLEI; BEHAVIOR OF THE SPHERE SUBSTANCE; ORIGIN OF THE CLEAVAGE. CEN- ARO SOMES oo occcececcecscseeecdes ewan wctsesen de cucesrsecesheeet artes ste ee nanan Rae eee pemareasrs 245 Ti) @PSCLV ACO eee oe cess onan canara achat ono aa ea eee aes toeaeees 245 2. Literature and Theory of Fertilization. ............---.-:-1-2ee-errees 250 IV. MovEMENTS OF THE FIRST CLEAVAGE SPINDLE. FIRST AND SECOND GTR MVIC ES occ eee caa ee nccde cee ced apse see cencsn cay debe nee raeeeeam ta een ae na V. CONCERNING THE SPHERE SUBSTANCE ©....-2..----:-2--eceesessesesereesereneeceesennecrscs 256 VI. Two RECENT THEORIES OF UNEQUAL CLEAVAGE .....----:-1--s-eoeeseesererteeteees 258 VII. ORGANIZATION OF THE EGG .....-....------