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LANCASHIRE SEA-FISHERIES LABORATORY

UNIVERSITY COLLEGE, LIVERPOOL,

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SEA-FISH HATCHERY, AT PIEL..

DRAWN UP BY

Professor W. A. Herpman, D:Sc., F.R.S.,

Hon. Director of the Scientific Work :

‘Assisted by Mr. AnpreEw Scorr and Mr. JAMEs JOHNSTONE. |

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a WITH NINE PLATES, AND OTHER ILLUSTRATIONS.

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Report oN THE InvestiGarrons carried on during 1900 in
. connection with the Lancasnire Sa - FIsHerres
Laporarory at University College, Liverpoo!, and
the Sea-Fisu Harcuery at Piel, near Barrow.

Drawn up by Professor W. A. Herpman, F.R.S., Honorary
Director of the Scientific Work ; assisted by Mr. ANDREW
Scorr, Resident Fisheries Assistant at Piel, and Mr.
JAMES JOHNSTONE, B.Sc., Fisheries Assistant at Liverpool.

With Nine Plates, and other Illustrations.

: CONTENTS.
. Introduction and General Account of the Work — - = ]

1

2, Required Survey of Fishing Grounds © - = : - 16
3. Fish Hatching at Piel - 2 2 - = = 31
4. Note on the Spawning of the Mussel — - - - . 36
5. Statistics of the Mersey Shrimping Grounds - - : 39
6. Report on Deposits and Shrimps — - - - - : 56
7. Note on a Sporozoon Parasite of the Plaice — - - - 59
8. On the Fish Parasites Lepeophtheirus and Lernca- - 63

Inrropuction AND GENERAL ACCOUNT OF THE Work.
Ixy the main the work of the past year has been
similar in its nature to that of the previous one, and has
consisted in: —

(1) The hatching operations and other work carried out
at Piel by Mr. Andrew Scott;

(2) Laboratory investigations by Mr. Johnstone at
Liverpool ;

(3) Certain observations at sea taken from the steamer,
at Piel, at the Isle-of-Man, and at various other points in
the district, by Mr. Dawson, Mr. Ascroft, and others—all
discussed and reduced to order at the Liverpool
Laboratory ;

(4) The work of the circulating Fisheries Kxhibit :

(5) Practical laboratory classes at University College,

Liverpool, for fishermen ; and

2

-_

(6) Various memoranda and reports that I have had
oceasion to address to the Chairman and Committee
during the year.

I shall remark upon some of these matters here, and the
others will be treated more fully in the separate sections
which follow. Last vear I commenced the plan, which I
hope to be able to adhere to, of having in each annual
report a detailed account of some animal of local economic
importance. It was then a memoir on the common
Cockle, by Mr. Johnstone; this time it is a full account
of two closely allied and very important Fish-Parasites,
Lernea and Lepeophtheirus, by Mr. Scott; while next year
it will be the memoir on the Plaice by Mr. Cole and Mr.
Johnstone, for which the plates are already drawn. Mr.
Scott’s remarks upon the effect which the fish-parasites
have on their hosts, and upon their nutrition and mode of
life, will be found of interest. The preparation of this
account of the fish-parasites has occupied a large portion
of Mr. Scott’s time during that period of the year when
hatching operations were not in progress.

An account of the hatching work will be found at p. 51.
The plan of storing up spawning fish* in the tanks in place
of trusting to the steamer for supplies has been most
successful, and the increase from the three and a half
millions of the previous year to fourteen millions of
young fish set free this vear is most satisfactory. For the
rest, Mr. Scott’s time has been filled up by collecting and
observing, by giving demonstrations to parties of fisher-
men, by experiments with shellfish, and by various other
pieces of useful work. The determination of the spawn-

* We had over 100 adult flounders in the tanks. I see from the Report
of the Scottish Sea Fishery Board that in their first year’s work at their
new hatchery at Aberdeen they had 400 spawning plaice, from which over
16 millions of fry were hatched. The female flounder, however, produces
about three times as many eggs as the plaice.

»)
o

ing times and the habits of the mussel at Piel will be
found on p. 56.

Mr. Johnstone's time—in addition to helping me with
general work, correspondence, the examination of any
specimens that arrive, the preparation of ‘‘ memoranda”
throughout the year, and of this Report—has been largely
taken up with arranging and superintending the removal
of the travelling Fisheries Exhibit from place to place.
The packing and unpacking of specimens, the renewal of
labels, &e., takes up a good deal of the time of both Mr.
Johnstone and of the fisheries laboratory boy, W. Raw.

The Exhibit, it will be remembered, after being at
Liverpool, Salford, Preston and Bolton, was at University
College in the winter of 1899-1900. = In March it was
removed to St. Helens, where it remained at the Public
Museum till November. The Curator, Mr. Alfred
Lancaster, has sent me a letter on behalf of his Museum
Committee, tendering their thanks to the Lancashire Sea-
Fisheries Committee for the loan of ‘‘ the very interesting
and instructive collection of Sea-Fisheries Exhibits.”
He states further that “the exhibition was visited by
upwards of 16,000 persons,” and he refers to the use
which school teachers made of the exhibition as the subject
of object lessons.

It will be remembered that a couple of years ago some
desire was expressed to have the exhibit at Barrow,
but negotiations eventually broke down. Mr. Scott has
since suggested that if the cases were exhibited for a time
in the large laboratory at Piel, that might serve for
visitors from Barrow and from the neighbouring fishing
villages. Accordingly in November the collection was

transferred to Piel, and is now on exhibition there.*

* Any other Museums or public Institutions desiring to have the
Fisheries Exhibit on loan should apply for a copy of the conditions and
regulations.

4

During the past year the following have occupied work
places in the laboratory at Piel for the purpose of carrying
on Zoological investigations : —
Dr. F. W. Gamble, Owens College, Manchester.
Working at Crustacea.

Dr. J. T. Jenkins, University College, Liverpool.
Working at digestive glands of Oyster.

Mr. F. H. Smith, B.Sc., Barrow-in-Furness.
Working at Algee and Diatoms.

Mr. J. E. Turner, B.A., Barrow-in- Furness.
Working at Marine Zoology and Fisheries.

Mr. John Graham, B.Sc., Barrow-in-Furness.
Working at Marine Biology and Physics.

These gentlemen have sent me short reports upon their
work, in which they express their thanks to the Com-
mittee and their appreciation of the facilities given by
the institution and the help rendered by Mr. Scott.

Parties of fishermen from Bardsea and Baicliff have
been brought on various occasions by Rey. R. B. Billinge
and Rev. Dr. Hayman, when explanations and demonstra-
tions were given by Mr. Scott and Mr. Johnstone. Many
other visitors, more or less connected with fisheries and
scientific work, including Mr. A. Milman, C.B., Mr. J. B.
Feilding, Mr. J. Fell and other members of the Sea-
Tisheries Committee, and the members of the Barrow
Field Naturalists’ Club, have been shown over the estab-
lishment, and have had the operations explained to them.

I regret that the applications for the two £60 Scholar-
ships for higher education in Fisheries Science, each
tenable for two years at University College, Liverpool,
which had been offered by the Lancashire County Council,
were most unsatisfactory. Only one candidate applied,
and from his defective preliminary education he was
evidently quite unsuitable. This unfortunate result was

~

apparently due to want of information among the higher
schools in the county of the advantages to be derived from
these scholarships. Several suitable candidates were
heard of when it was too late. Considering the increase
of work and of interest in Marine Biology and its appli-
eation to Fishery questions of late years, it will be very
unfortunate if this important experiment is allowed to
lapse merely because of the absence of candidates in the
first year, before the scheme was sufliciently known.

In addition to these scholarships, the County Council
granted last year a sum of £100 for studentships to enable
fishermen to undertake a short course of practical instruc-
tion in the Zoological Department at University College,
Liverpool. It was, after careful consideration by a Com-
mittee, decided to send 20 elected fishermen representa-
tive of different centres and branches of industry, to
University College; each to have a fortnight’s instruction,
and the sum of £5 to be paid to each man to cover his
travelling expenses and board and lodging, and to re-
imburse him to some extent for what he might have
lost by not following his ordinary vocation during the
two weeks. These laboratory classes were held in
February and March, 1900; and the main part of the
work was carried on by Mr. Johnstone under my personal
direction and supervision. The course was divided up
into ten days, the work upon which was as shown in the
following sections : —

1. Tue Common Mussen.—Structure (especially in regard
to feeding, breathing, reproducing and _ habits),
spawning and life-history.

2. Hapvpocx.—Structure, feeding, breathing, spawning,
and life-history.

8. Cras, Prawn, Surime and Lossrer.—Habits, food,
eggs, reproduction and life-history.

6

4. Surrace Lirz or Sea.—lownet gatherings, fish eggs,
diatoms, copepoda.
5. Fisnerres Muspum.—An examination of the cases in
the museum at University College.
6. Eprste Motiusca.—Oyster, cockle and mussel.
. Fish Parasrres.—External and internal, and their
hosts.

8. Fish SrructurE.—Cod—Also stages of growth and
changes in reproductive organs.

9. Foop or Fisues.—How to examine fishes’ stomachs
and determine principal food matters.

10. Eaes anp Larva Staces or Fisu.—How to dis-
tinguish them and where they are found. Also
egos of Shell-Fish and Crustacea.

The whole course was made entirely practical in character.
Each man examined everything for himself. The course
was preceded by an introductory address by myself, and
I finished it with a short concluding lecture.

The Committee may like to have recorded here the list
of those who attended this first laboratory class for fisher-
men. It is as follows: —

In Febrnary—

John Wright, Southport.
Wilham Wright, Southport.
George Alexander, Morecambe.
Luke Woodhouse, Morecambe.

In March—

Walter Baxter, Morecambe.
Robert Gardner, Morecambe.
James Allan, Morecambe.
Thomas Wilson, Morecambe.
Edward Woodhouse, Morecambe.
Jolin Wright, Southport.

Albert Robinson, Southport.

=

(

John Rigby, Southport.

R. Rimmer, Marshside.

R. Ball, Marshside.

W. Houldsworth, Marshside.

John Hardman, Lytham.

Thomas Clarkson, Jun., Lytham.

John Parkinson, Lytham.

Robert Wright, St. Annes.
Mr. Dawson has already reported as to the way in which
the men appreciated these practical classes, and he has now
written to me of the benefit which, in his opinion, the
studentships were to the fishermen. He says: * From
Morecambe, Lytham, St. Annes, and Southport and the
district I have heard the work spoken of with praise, and
how satisfied the men were. I have also had several
enquiries as to when more classes would be held, as the
men wanted to go to them.” And again, “On all sides
I am informed that the fishermen were most interested
in the work, and that if any more studentships are offered
the difficulty will be not to get men to go, but to choose
from amongst the number of applicants.”

In October some questions arose in regard to the con-
dition of the Oysters on the bed at the mouth of the
Ogwen River, near Bangor, so I arranged that Mr.
Andrew Scott, from Piel, should visit the locality, take
certain observations, and bring back samples of oysters,
of deposits, of water and of microscopic food materials in
the neighbourhood of the bed, for examination in the
Liverpoo] Laboratory. Mr. Scott carried out his inspec-
tion on October 9th, along with Mr. Jones, the Head
Bailiff of that division, and brought back material which
I examined with him. The oysters are Ostrea edulis in
yarious stages of growth (from one to three inches in
diameter), and are evidently living and reproducing

8

between tide-marks. Many were attached to stones. It
is consequently a natural oyster-bed, but it is evident
from the condition of the specimens examined that there
is not sufficient food on the ground or in the water to
constitute the locality a good fattening area. The bodies
of the oysters were found to be very thin and in poor
condition generally.

The bed is entirely covered at each tide, and only ebbs
completely dry at low water of an eighteen-foot tide with
favourable weather. The bottom is hard, being composed
of gravel and shells, with some fine mud_ between.
Samples from the ground and from the water showed that
diatoms and other minute forms of life which are so
necessary in the case of a flourishing oyster fishery were
so few as to be almost absent. It is quite possible that
during summer, at the breeding season, more microscopic
food may be present—perhaps due.in part to the river,
and it is probable that the bed in favourable seasons
forms a good enough spatting ground; but all the
evidence before us shows that it is not a favourable
locality for the rearing and fattening of oysters. Pro-
bably the best plan would be to use it as a place for the
production of spat, from which a certain proportion of the
young oysters should be transferred to other localities
where they can be more satisfactorily nourished. I think
it worth while to try whether if would not be possible
by the judicious placing of tiles and other collectors,
and by certain obstructions in the water channels over
the bed, to largely increase the deposit of spat; and I
should recommend that some of the half-grown oysters
be removed to certain grounds in the neighbourhood of
Piel, on the south and south-east sides of Foulney Island,
which we know to be richly supplied with diatoms and the
othe unecessary food, in order that their growth may be

4)

watched and compared with that of similar oysters left on
the bed at Bangor.

I think it is a question whether the spat on the Ogwen
bed is derived wholly from the old oysters in sight, or
whether its source may not be individuals in deeper water
somewhere in the neighbourhood. I propose to visit the
bed myself during next spawning season in order to try
to settle this and several other questions in connection
with the reproduction and spatting of the oyster.

The further point has been raised that the Ogwen River
oyster-bed may be liable to sewage contamination from
the drains of Bangor. The observations made by Mr.
Scott and the samples brought back by him, although not
absolutely conclusive on this poimt, certainly suggest
material of sewage origin, and it is difficult to believe that
under certain conditions of wind and tide the bed can
escape from pollution by the town drainage. However,
this is a matter that may require further investigation,
and in any case it does not affect the value of the locality
for the production of spat and the rearing of young
oysters which may be fattened elsewhere before being
placed on the market. The whole question of the dis-
posal of sewage and the pollution of our rivers, estuaries
and sea shores is one that is in an unsatisfactory condi-
tion, and requires more careful consideration than it has
yet received.

I desire to draw the attention of the Committee to some
points In connection with the so-called * Bacterial treat-
ment” of sewage (by coke filter beds or by septic tanks),
which is now being adopted in various parts of the
country. The recently published report to the London
County Council by Professor Clowes and Dr. Houston
shows that the effluent discharged after such treatment,
although it may seem pure and have some objectionable

10

features removed, contains practically all the bacteria
found in the crude sewage.* From the public health
point of view the clarifed effluent apparently may be
little if at all better than the original untreated sewage.
Under these circumstances I would ask—is it not a very
serious matter that such an effluent should be allowed to
discharge anywhere in the neighbourhood of shell-fish
beds, or where any fishery contaminationst could take
place? I may also remark in passing that however pure
such an effluent may look in mixing with the sea, bathers
should be warned against its dangers. Another point
with which we are not directly concerned at present,
although it is of great interest to the scientific man, and
may be of practical importance to the country, is whether
enormous quantities of valuable fertilising materials
which ought to be applied to the land are not now being
wasted in the sea. We can leave the bathers to the
sanitary authorities, the question of fertilisers is one for
the chemist and the agriculturist; but we are directly
concerned with the coast fisheries, and I would urge that
the Committee, and all fisheries authorities, should give
most careful consideration to the relations between shell-
fish beds and any sewage effluents, whether “ treated ”
or not.

Early in the year | asked Mr. Johnstone and Dr. J. T.
Jenkins, who was at that time working in my laboratory
at Fisheries subjects, to devote a certain amount of time
in each week to a careful examination and classification
of all our fisheries statistics (accumulated during eight or
nine years), with a view to the drawing of any conclusions

* London County Council Bacterial Treatment of Crude Sewage. Third
Report by Dr. Clowes and Dr. Houston, 1900.

+ Lam not alluding to the conditions in the Thames, which I do not
know personally. It may be that no difficulty arises there. I am speak-
ing of the question generally, as such effluents may be likely to increase
around our coast, and will require careful attention.

11

which might be indicated. It has been a lengthy and
troublesome piece of work, lasting most of the winter,
and over a thousand sheets of statistics have been very
carefully analysed. The results, I regret to say, are by
no means commensurate with the labour that has been
expended. For the majority of fishes and localities the
statistics are so defective or so vitiated from one cause or
another that we felt that no reliable conclusions could be
drawn. In fact it was decided in the end that the only
area in regard to which we had sufficiently detailed
information was the shrimping area at the mouth of the
Mersey. Hence the article on that area by Mr.
Johnstone and Dr. Jenkins which I include in this Report
(p. 39).

But it must not be thought that I regard the
time and labour which these gentlemen have spent in
trying in vain to draw conclusions from the remaining
statistics as lost because they have deduced nothing which
we are able to publish yet. Var from it: it has led to
the very important conclusion that the system we have
hitherto employed on the fisheries steamer and elsewhere
in the district is really inadequate, that the statistics are
not taken sufficiently often or with sufficient regularity,
and are not taken with sufficient detail. If this discovery
leads to the adoption of a better scheme (such as the one
I suggest below, p. 24), and to its faithful performance in
the future, the disappointment we have had in finding
one after another of the series of statistics broken by
unfortunate omissions* will be mitigated, and we may
then hope that the next decade will be so traversed by

*Due to the circumstance that we have only one small steamer avail-
able for all the police and other administrative work of a large district, in
addition to what I cannot but regard as of still greater importance—viz..,

the observational work on the condition and variations of the fisheries and
their causes,

12

observations as to leave no doubt as to the conditions of
fisheries and the progress of events.

I have spoken of the statistics as being incomplete and
inadequate ; but although they do not give us the informa-
tion we expected, they are by no means useless. Every
correct observation, and there are many thousands of such
in our sheets, is of value even if it deals with isolated
facts. It may give useful information which may be
required at any time, and we hope that all these observa-
tions may fit in with our future records of facts, and so
play their part eventually in the elucidation of important
points.

Statistics obtained as the result of investigations made
with regularity at fixed spots in accordance with a definite
scheme are the more necessary since such very different
conclusions have been drawn of late years from the com-
mercial statistics as supplied by the Board of Trade. One
of the most recently expressed of these is an article by
Mr. Walter Garstang, entitled ‘The Impoverishment of
the Sea,’ in which the conclusion is arrived at that the
fish population is decreasing because although the total
catch increases year by year, the take per unit of catching
power diminishes. I do not quarrel with Mr. Garstang’s
conclusion, but the argument by which he arrives at it
does not carry conviction. Except on ground where
there is practically an unlimited number of fish, doubling
the number of boats would surely not lead to doubling
the catch, and consequently as the boats increased
the take per boat would diminish to some extent without
there being necessarily a permanent reduction of the fish
population.

Turning to another important side of fisheries work,
namely, experimental investigation, it is of interest to
note that in the twenty-fifth Report of the United States

13

Commission of Fish and Fisheries, just published,
Commissioner G. M. Bowers states, ‘‘ Our leading fishery
product, the oyster, worth about $14,000,000 annually, is
readily susceptible of increase by methods of cultivation,
and each season shows a larger proportion of the market-
able output taken from planted grounds, thus insuring a
permanent and increasing supply.” He states further
that while the natural supply of oysters is surely becoming
exhausted, the areas of the sea-bottom which are being
artificially cultivated are becoming more and more pro-
ductive, and certain States which have adopted * advanced
cultural methods” are “reaping important pecuniary
returns.”

Then again, “There is unmistakable evidence of an
increased abundance of Cod in the inshore waters along
the entire coast from Maine to New Jersey. This may,
without hesitation, be attributed principally to the work
of artificial propagation centering at the stations of the
Commission at Gloucester and Woods Hole.”

The Commissioner urges that new work should be
undertaken for increasing the lobster supply by artificial
propagation. He states:——‘‘ During the past five years
over 500,000,000 young lobsters have been artificially
hatched by the Commission and planted on the East
Coast. As practically all the eggs from which these were
produced would have been destroyed had not the Com-
mission purchased the egg-bearing adults from the fisher-
men, it can hardly be doubted that these operations have
had a decided influence on the supply, but they have not
as vet seemed to arrest the decline, in the face of over-
fishing and the destruction of short lobsters and brood
lobsters carrying eggs.” I have had an interesting letter
from Professor H. C. Bumpus, who has charge of the

work at Woods Hole, telling of the details of the methods

l4

he has devised “for the rearing of young lobsters up to
the fourth moult, at which time, as you are well aware,
the animals become pugnacious, their shells become hard,
and they adopt many of the peculiarities of habit of the
adult, and, moreover, they appear to be hardy and well
able to look out for themselves.” Professor Bumpus goes
on to say— “ For convenience I have termed this stage
the ‘ Lobsterling’ stage, and I am inclined to think that
if we should succeed in raising even a small percentage
of the fry to this lobsterling stage before berating them,
we might accomplish for the lobster fishery what the
release of ‘ fingerlings’ has accomplished for the trout
fishery. Inasmuch as you are experimenting in the same
line, and since one of the most important, and at the
same time one of the most inviting problems of marine
biology to-day is the preservation of the lobster industry,
I take the liberty to tell you of our experiments during
the past year, and if vou should have opportunity or
inclination to adopt similar methods, I should be very
glad to learn of your results.” The further details which
are given have been sent to Mr. Andrew Scott for use in
his work at Piel. During last summer the disturbance
of work consequent upon the sale of the old steamer and
the purchase of the new one prevented any supply of
lobsters from reaching the hatchery until it was too late,
but during the coming season we hope to resume work
upon the hatching and rearing of this very important
economic animal.

In concluding this general part of the Annual Report
I desire to draw the Committee's attention once more to
the pressing need of a pond or some large open-air tanks
at Piel, both for the reception of spawning fish and also,
later in the season, for the purpose of rearing the fry
obtained by the hatching operations, The tanks would

15

also be useful during the remainder of the year for many
other purposes.*

In the special parts of this Report which follow will be
found: —Mr. Scott's account of the hatching operations
at Piel, with a description of the new apparatus he has
devised for keeping the water in motion: Mr. Johnstone's
statistics of the Mersey Shrimping Grounds: a report
upon the deposits on these grounds in relation to shrimps
and young fish; a note on a new parasite in the plaice ;
Mr. Scott’s memoir on the two Copepod Fish-Parasites ;
and an article I have thought it well to write on the
necessity for a more detailed examination of our fishing
grounds, with an outline of a scheme of observational
work for use on board the steamer, to which I desire to
call the special attention of the Committee.

W. A. HerpMAN.
Universtry Couuecr, Liverroon,
January, 1901,

* These were referred to in detail in last year’s report, at p. 10

16

REQUIRED StuRVEY OF oUR FiIsHinG GROUNDS, WITH
New ScHEME oF Work aT SEA.
By W. A. Herpman.

In last year’s Report, at p. 14, in an article on ‘‘ Sea-
Fisheries Conferences and the need of a ‘ Census’ of our
Seas,’ I pointed out that *‘ what we stand most in need
of at present is full and accurate statistics in regard to
our fisheries, and much more detailed information than
we have as to the distribution round the coast both of
Fishes, in all stages of growth, and also of the lower
animals with which they are associated, and upon which
they feed.” I then proceeded to propose a scheme of
investigation which I characterised as “the nearest
possible approximation to a census of our seas—beginning
with the territorial waters and those offshore grounds
that supply them and are definitely related to them.”
The work would be partly of a statistical nature and
partly scientific observations and investigations, and
it seems clear that it is only by such methods that we
can hope to settle many important fishery questions.

I do not think that I am under-estimating the magni-
tude, the difficulties and the probable imnerfections of
such a scheme as I propose. I am aware that all we can
hope to attain is an approximation, but even a rough
approximation will be of use, and if carried out on the
right lines it is an approximation which will approach
more and more nearly to the truth with each successive
year of work.

The fishery statistics collected and published at
present by the Board of Trade are, I contend, inadequate.
They do not give us the information we require. The
system does not seem to be designed so as to realise and

Mv

tackle the problem which ought to be tackled. What we
should aim at ascertaining is not what a fisherma
catches, but what there is for him to catch. We must in
fact get series of accurate observations which will give
us fair samples of the more sedentary populations of our
seas on the different grounds, such as trawling grounds,
shrimping grounds, nurseries and spawning banks, at the
different seasons. I have spoken of this in brief as
to aim at taking an approximate “census”’ of the sea,
but that, of course, is too ambitious a word, and indicates
an exactness to which we probably could never hope to
attain. Still the word serves to remind us of our
approximate aim, and if we can even determine the
numbers of a species on an area between wide limits, it
will be of great importance.

The investigation is, of course, beset with difficulties,
but they are not insuperable. One great difficulty is to
determine to what extent we can safely draw conclusions
from our observations. In speaking of this matter
recently to a Liverpool audience I made use of a homely
illustration, which may be worth repeating here as a
possible help to some readers in realising the problem. I
compared the investigation to the case of an aeronaut in a
balloon trawling along the streets of Liverpool through a
thick fog. We may suppose that a drag in the neighbour-
hood of University College would yield some students—
male and female—and a professor; one somewhere about
the docks would doubtless capture some sailors, dock
labourers, and a stevedore or two, while a lucky shot
opposite the Town Hall might bring up a policeman, an
electric car, and a couple of Aldermen. Now, if such
experiences were repeated over and over again, would the
conclusions that might naturally be drawn by the intelli-

gent aeronaut as to the relations between organisms and
B

18

environment in Liverpool be correct ? The observed
association of students with a professor, and of both with
a college, would be justifiable. It would be correct to
conclude that sailors, dock labourers and_ stevedores
frequent the docks, and that Aldermen have some con-
nection with a Town Hall; but the fact that electric cars
are also abundant in front of the Town Hall is non-
essential, and any conclusion such as that Aldermen and
electric cars are usually associated with the same habitat,
and are in any way inter-dependent, would be erroneous.

We can imagine many other cases of this kind where
appearances might at first be deceptive, and false
inferences might be drawn from observed facts. On the
other hand, some true conclusions would be clearly indi-
cated; and I do not doubt that it 1s much the same in
our investigations as to the condition and population of
the sea-bottom. It is probable, moreover, that the false
inferences would be corrected by the accumulation of a
greater number of statistics. It might be made out from
further observations that electric cars are liable to become
massed in various parts of the town, and have no necessary
connection with Aldermen, and that policemen are widely
but sporadically distributed. The more numerous our
observations, the more our statistics accumulate, the less
chance is there of erroneous conclusions.

My contention, then, is that such an investigation of
our seas must be made, that it is urgent and should be
made now, and that the Irish Sea is favourably situated
and circumstanced at present to be made a test case before
undertaking the much wider and still more difficult
expanse of the North Sea, complicated by international
questions. The Irish Sea is of moderate and manageable
dimensions (see fig. p. 19). It is all bounded by British
territory and by sea fisheries authorities who might agree

.

1g

as to their regulations. It is a “ self-contained ”’ fish area,
containing spawning banks, feeding grounds and
“nurseries.” It has several laboratories (Liverpool,

co Hilbrel..
o

Plan of the Irish Sea, showing depths of water. The deepest shading
is from 50 to 80 fathoms.

Dublin, Port Erin and Piel) on its borders which would
form centres for investigation, and it is controlled by
powerful sea-fisheries authorities, two of which
at least (Lancashire and Ireland) are provided with
excellent steamers which might combine in the work.
All that is required, beyond a carefully considered scheme
of work, is authority from the Government to the local
Committees to carry out such work, and a subsidy for say
five years to meet the increased expense.

The Select Committee of the House of Commons, which
considered the Undersized Fish Bill last summer, clearly
recognised in their report the need of some such scheme

20

of investigations, and they recommended that a Govern-
ment Department should be equipped to carry it out. I
am of opinion that the matter would be better entrusted,
as I have indicated above, to the local Sea-Fisheries
Committees. However, there are the two methods—

1. To form a properly equipped Government Depart-
ment (comparable with the Geological Survey),
with laboratories and steamers and a scientific
staff competent to tackle the scientific problems
involved. This is the method adopted in the
United States and elsewhere.

2. The other, and perhaps the more characteristically
Knglish method, is to give fuller powers to the
local authorities, and to encourage them to spend
money on the necessary investigations in their own
districts.

Correct statistics are very important, and they could
probably be taken at least as efficiently by the sea-fisheries
officers, under the control and supervision of the Fisheries
Superintendent in each district, as by the Board of Trade
officials; but no system for the collection of statistics even
if much better than that now employed can take the place
of a scheme of periodic scientific observations and inyesti-
gations such as I desire to see carried out all around the
coast by the local Sea-Fisheries Committees.

It is, I think, agreed on all hands that what is most
urgently required is facts—but facts that can only be
ascertained by continuous work on a sufficiently large
scale. The Select Committee on the Sea-Fisheries Bill
last summer reported that the Scottish Fishery Board’s
‘investigations have been hampered by inadequate means.
They have not much money at their disposal, and the
vessel which they have for the purpose of scientific inves-
tigation is undoubtedly too small.”

But, incredible as it may seem, Mngland has no vessel
at all, large or small, devoted to the purpose of such
investigations. How long will this absurd condition of
affairs be allowed to continue in this rich country, with
its boasted advanced position, enlightened views and keen
eye to practical applications’ Not only other civilised
countries but even some of our own colonies are far in
advance of us in the public utilisation of Marine Biolo-
gical investigations.

Norway is a poor country, but, in some directions at
least, an enlightened one. Here is the latest item of
news in regard to her fisheries investigations : —‘ The
Norwegian Government has built and fitted out a steain
vessel for the express purpose of marine scientific
research, and has placed her, as well as a trained staff of
assistants, in charge of Dr. Johan Hyjort as leader of the
Norwegian Fishery and Marine Investigations. The
vessel herself, the ‘‘ Michael Sars,” has been constructed
in Norway on the lines of an English steam trawler—that
type of boat being regarded as the most seaworthy and
suitable for such an expedition—but considerably larger,
being 132 feet in length, 25 feet beam, and fitted with
triple-expansion engines of 300 horse-power. The fishing
gear includes znter alia, trawls, nets, and lines of all kinds,
with massive steel hawsers and powerful steam winches
to work the heavy apparatus; while the numerous
scientific instruments are of the very best and latest
description. The expedition left Christiania in the
middle of July on what may be termed its trial trip along
the Norwegian coast (accompanied for part of the time
by Dr. Nansen, who was desirous of testing various
instruments in which he had made improvements),
and has just sailed from Tromsé on a lengthy cruise to
the North Atlantic and Arctic Oceans. Dr. Hjort has

os)

od hl

already added so much to the knowledge of pelagic fishes,
their life, habits, and the causes affecting their migra-
tions, that, with the means now at his disposal, a con-
siderable amount of valuable information will probably
be gained which will prove of service to the fishing
industry of all nations.”

What Norway can do, surely the whole western sea-
board of England, from Cumberland to South Wales, now
united in one Sea-Fishery District, ought to be supplied
with, or be able to afford. Surely we may hope to see in
the immediate future a steamer, at least of the size and
equipment of a modern steam trawler, devoted solely to
that combination of scientific and economic oceano-
graphic investigations in the Irish Sea of which every
conference of Fisheries Authorities, Commissions and
Select Committees of recent years has had to deplore the
absence.

In addition to the investigation of the bottom by
dredging and trawling, the plankton in the surface and
other waters of the sea would require periodic examina-
tion. This matter has been discussed fully during
the past summer, both at Port Erin and Liverpool,
amongst our local naturalists, some of whom have had
much experience of late years in plankton work. In
order to get an adequate idea of the distribution of the
minute floating organisms of our seas, we should certainly
require to have weekly observations (or possibly even
twice a week) taken, at both surface and bottom, at
certain specified stations round the coast, of which we
should recognise four as being necessary in the Irish Sea,
and about 15 round the whole British Coast. The
Lancashire Naturalists are willing to play their part in
any such general scheme, but in the meantime we are
going on with the work in our own district. Mr. Isaac

Thompson at Liverpool, Mr. A. Scott at Piel, Mr.
Chadwick at Port Erin, and Mr. Ascroft at Lytham, are
all at work, and we have drawn up and agreed upon the
following common list of pelagic organisms the
occurrences and relative abundance of which in the
various parts of our district will be periodically registered
for each week in the year: —

Fish eggs, fish larvee, Appendicularia, gastropod larve,
larval lamellibranchs, larval crabs, other larval crustacea,
Alteutha interrupta, Jonesiella hyene, Acartia sp.,
Temora longicornis, Isias clavipes, Centropages sp.,
Euterpe acutifrons, Calanus finmarchicus, Anomalocera
patersoni, Pseudocalanus elongatus, Oithona spinifrons,
eggs and larvee of copepoda, Podon intermedium, Hvadne
nordmanni, larval Cirripedia, Echinoderm larve, Autoly-
tus sp., Tomopteris onisciformis, larval Polycheta, Sagitta
sp., larval Polyzoa, Ctenophora (state which), Meduse
(do.), Medusoid Gonophores (do), Noctiluca sp., Ceratium
sp-, Rhizosolenia sp., Chaetoceros sp., Biddulphia sp.,
Coscinodiscus sp., Nitzchia sp.

Mr. Ascroft is especially devoting his attention to our
plankton work, and is now receiving and examining
collections from various parts of the district. We hope
that he will be able to contribute an account of these to
our next Report.

With a view to making the best use of the time until
the “census” investigations which 1 have recommended
above are started, or until a steamer is obtained solely for
scientific work in the Irish Sea, I drew up in October
the following scheme of observational work which I hoped
would be carried out by the new Lancashire Sea-F isheries
steamer when she started on her routine work. The
scheme was submitted to the Committee, and although it

has not yet been formally adopted for execution, I hope

24

that it will now, in the hght of the arguments as to the
importance of such work which | have urged above,
receive further consideration, and become as soon as
possible an important part of the monthly work of the
steamer. I reprint the scheme verbatim from the docu-
ment privately issued in November : —

* Laneashire and Western Sea Fisheries.

“Dr. Herdman’s Scheme of Investigations.

‘Preston, 1900.

* To the Lancashire and Western Sea Fisheries Commuttee.
‘From Professor W. A. Herdman, D.Sc., F.R.S.,
‘“ University College, Liverpool,
“ October, 1900.

“If there is one point more than another that the
numerous Fisheries Congresses and Enquiries of recent
years have made quite clear, it is that what we now need
most for a proper understanding of the condition of the
Sea Fisheries of North-Western Europe is a much more
detailed knowledge than we have of the populations of all
parts of our seas. Such knowledge can only be obtained
by trawlings and other observations conducted regularly,
frequently, and according to a definite scheme. Accurate
practical work of this kind is usually called * scientific
investigation, but it must be remembered that science 1S
merely organised common-sense: and that any observa-
tions made accurately, and intelligently directed towards
the ascertainment of facts, are scien'tific. The Select
Committee of the House of Commons refused, last
summer, to recommend the Sea Fisheries Bill because of
the want of statistics based upon such ‘scientific investi-
gations.’ It is thus evident that the systematic scientific
investigation of our seas is of practical importance, and

25

is very urgent, since Fisheries legislation is blocked for
want of the information which such investigations alone
can give.

* A scheme of scientific work has been carried out for
some years on board the ‘John Fell, but the observations
—although useful for many purposes—have been neither
sufficiently numerous nor sufficiently regular to admit of
reliable conclusions as to the abundance, movements, and
life-histories of the fish being drawn. Now that a more
efficient steamer has been obtained, I would urge strongly
upon the Committee the importance—and even necessity
—if we are to make any advance in our knowledge of
how and where fishes live in the sea, of devoting a certain
amount of the steamer’s time to the taking of regular
periodic observations at fixed points according to a
definite plan.

* After full consideration of what is desirable and what
is possible in our District, with a steamer which has also
to carry out police and other administrative duties, I have
drawn up the following, which I believe to be a workable
scheme, and one which is calculated to give us the kind
of information we require as a basis for the just and
adequate regulation and administration of our District.

“TT venture to think that if some such plan of observa-
ticns had been adopted fifty or even twenty years ago, it
is not too much to say that the results would be invaluable
at the present day to the Naturalist and to the Fisheries
Administrator alike. In face of the statistics so acquired,
many of our Fisheries questions could not have arisen.
There could no longer be doubt as to whether a particular
Fishery, or Coast Fisheries in general, had or had not
declined ; as to whether the destruction of immature dabs
benefitted or not the neighbouring population of young
plaice; as to whether solenettes can possibly interfere

26

with young soles of the same size; as to whether
‘nurseries’ are already overstocked with young fish, or
may with advantage be replenished as the result of arti-
ficial hatching operations.

“If public opinion has advanced, and _ Fisheries
administration is more enlightened now than it was fifty
or twenty vears ago, let us see to it that the reproach of
the nineteenth century is not continued on into the
twentieth. I submit this Scheme to the Committee in
the hope that they will authorise its immediate adoption
on board the steamer, with a view to starting the new
century well by having reliable and adequate monthly
Fishery Statistics taken for the first time in January,
1901.” “W. A. Herdman.”

“Suggested Scheme of Fishery Observations.

“Regular Monthly Observations (as far as possible
during the first week or ten days of each month) should
be made on the following five Stations—as shown on a
Chart marked by Mr. Dawson : —

Station 1.—Blackpoo] Closed Ground.

STaTion 2.—A similar area a little further South.
Station 5.—Mersey Shrimping Ground, Burbo Bk.
Station 4.—Outside N.W. Lightship to 20 fath. line.
Station 5.—Red Wharf Bay, Anglesey.

“Stations 1 and 2 are important for comparison with
one another; Station 5 gives information on shrimping
and immature fish questions; Station 4 is on interesting
ground, just outside the territorial waters; and Station 4
is an important trawling area in the newly amalgamated
Welsh portion of the District.

“The Observations made should include: —

I. Drags with the fish trawl and shrimp trawl.
II. Plankton collections with surface and bottom
tow-nets.

27

III. Physical Observations with thermometers,

hydrometers, &e.

I.—Fish and Shrimp Trawling Observations.

“ (a) Drags should be made under strictly uniform
conditions: that is, the same trawl net should
always be used, and the drags should be of
uniform length and duration, in order that
they may be as strictly as possible comparable
with one another. In addition to the fish
trawl, it would be very useful—especially at
Stations 1, 2, and 5—if a haul of the shrimp
trawl could also be taken.

“(b) Every drag should be recorded, irrespective of
the numbers of fish caught. A poor haul is
just as important for statistical purposes as a
successful one.

“(c) All the fish caught should be measured, and the
numbers of each kind and size accurately
recorded on a Form similar to the one
appended.

“(d) Two or three individuals of each of the more
important kinds of fish—such as plaice, sole,
cod, haddock—from every haul should be
weighed and measured separately. The
ovaries should then be taken out and weighed,
and the results recorded on the Form. Any-
thing noteworthy in the condition or
appearance of the ovaries should also be added.

‘(e) Mention should be made of any unusual fishes
or invertebrata taken in the trawl, and also of
any special abundance of common things such
as star-fishes, crabs, molluscs, jelly-fish,
zoophytes, worms, or other fish food.

28
Unusual specimens, or anything not recognised

should always be preserved for examination in
the Liverpool Laboratory.
II.—‘* Plankton” cor Tow-Net/ Collections.

* Tow-nettings should be taken along with every drag
of the fish trawl. One haul with a bottom and one with
a surface net should be made on each occasion. The
collections should be at once preserved in formaline
solution, and sent to the Liverpool Laboratory as soon as
convenient after landing. Extra tow-nettings should be
taken as frequently as possible. Al such observations
on the floating life of the sea (which includes the eggs
and the microscopic food of many fishes) are most useful.
Even short hauls of ‘half-an-hour’s duration, taken twice
a week, will probably suttice to give a fairly accurate idea
of the movements of the Plankton in the District.

TII.—Physical Observations.

(a) Spa Temperatures.—Surface and bottom obser-
vations should be taken at the beginning and
end of each drag. Bottom temperatures
should be taken with a reversing thermometer.

(6) Sprciric GRAVITY OF THE SEA WateR.—NSurface
and bottom observations should be taken at
the beginning and end of each drag. Bottom
observations should be made on samples of the
bottom water, taken with a Mill’s bottle.

“(¢) Arr TrmMprraturE.—One observation at the
beginning of each drag should be taken for
comparison with the sea temperature.

‘“(d) Bsrometric PressurE.—One observation taken

at the beginning of each drag is sufficient.

‘* (e) TRANSPARENCY OF THE SEA Water.—One obser-
vation should be taken at the beginning of

29

each drag, and if any notable change has taken
place in the water, a second observation should
be made at the end.

““(f) Tur State oF Wind, Tipe, SEA, WEATHER, &c.,
should be recorded on the Form supplied.

“The above scheme applies only to the work on board
the steamer. The observations carried on by the bailiffs
in inshore waters should, of course, be continued, and
weekly tow-nettings should be taken in each division of
the District.

“The Forms containing the results of the above obser-
vations should be posted to the Fisheries Laboratory,
University College, Liverpool, with the least possible
delay, as it is important that early information should be
obtained of any unusual occurrence or any change in the
distribution of fish and Plankton throughout the District.

“A copy of the Form upon which the observations
should be recorded is appended.”

[N.B.—The Form on p. 30 is a compressed version of the
original. |

30

Record of Observations made op Station No. Diatte

Positions at beginning and end of drag.

Description of net. Drscription oF CATCH,
Time net down, beginning and end of drag. Name of | Size in inches, Tot
fish. 4 6 |8,&c} No
State of tide at beginning of drag. : |
Weather. Sole
Wind. ‘| Plaice
. Depth during drag, beginning and end of drag. Dab
Nature of bottom. Flounder
General remarks. Lemon Sole
Cod
Whiting ...
Haddock . .

PHYSICAL OBSERVATIONS.

Skate

Transparency of water, beginning and end of drag.
Barometer, beginning of drag.

Air temperature, beginning of drag.

Si

Surface temperature of water, beginning & end of drag.

Any other food
fishes

Bottom temperature of water, do. g
er : Surface tow-netting— led
Specific gravity of surface water, do. Suriace tow et he =

up in Laboratory.
Specific gravity of bottom water, do.

General remarks.

Bottom tow-netting—To be filled

No. of fish

lo rst Wt. of | General up in Laboratory.

selected. Size. | Weight. Ovaries. |condition. I ; ‘ \ -@
Place
a es Beemer |} 3
Sole... Note any unusual ‘fishes ot

=n al be a iz invertebrates.

Cod i
i ae | en PP 2 ee | | |
Haddock..

a a

31

THe Fish HatcHery at PIs.
By ANDREW SCOTT.

In last year’s Report, p. 25, it is stated that white flukes
were being collected and kept in the tanks at Piel in the
hope of their spawning in the spring. Before the end of
January 150 fish had been placed in the tanks. The
ratio of the sexes was three females to two males. The
fish were all collected in Barrow Channel by the local
police boat in charge of Mr. Wright.

The fish thus collected, owing to unforeseen circum-
stances, proved to be the main source from which the
egos were obtained for incubation during the spawning
season of 1900. The rough weather which prevailed
in the earlier part of the year, along with the necessary
arrangements for the sale of the steamer, which took place
in the middle of the spawning season, prevented the
steamer from doing very much to help in collecting eggs
at sea or from the trawlers.

In the earlier part of the year, however, the steamer
made a number of visits to the spawning grounds. On
three occasions eggs were obtained, twice from the Clyde
and once from fish caught by the trawlers working on
the offshore grounds. The first eggs, collected from fish
caught in the Clyde, March 12th-16th, were practically
all lost through the rough weather encountered on the
homeward journey. The second lot, also from the Clyde,
arrived on March 28th in much better condition, and
yielded good results. The third lot, from the offshore
grounds, collected April 5th to 6th, were equally satis-
factory. Altogether 2,454,800 fry were hatched and set
free from the eggs collected by the steamer. A number
of nearly ripe plaice were brought from the Clyde on the
first visit. Some of these spawned in our tanks, vielding
an additional 65,000 fry.

32

The first fertilised eggs from the flounders stored in
our tanks were obtained on March 8th. These fish con-
tinued to supply eggs until the middle of May, and from
these nearly twelve millions of fry were eventually set
free. The total number of living eggs placed in the boxes
was 16,000,000, and the number of fry set free 14,144,400,
so that the loss during incubation was only a little over
11°5 per cent., a very low percentage. The duration of
incubation was 16 to 17 days for the plaice, cod, and
haddock, and 7 to 9 days for the flounder.

The success of the incubation was probably due to the
healthy condition of the eggs dealt with, and also to the
employment of apparatus giving a rocking motion to the
hatehing boxes (see below, p. 33).

The following list gives the number of fry set free,
and the dates on which they were liberated. Those
marked with an asterisk were hatched from eggs collected
by the steamer. All were placed in some part of that
wide area of our sea known as Morecambe Bay.

March 21. 1,126,000 flounder.
31. 848,000 45

99

Aprils «2: 598,000 <i
” 2: 20,000 haddock.*
Ay dD. 520,000 flounder.
6 5. 15,500 plaice.*

5. 23,000 § ox;

sg 9: 934,400 _,,
fs 9. 90a;000), 15 oF
A: 12. 8503200 4 4
i iz: 219,800 cod.*
. ite. 285,700 haddock.*
“ 1 87,500 plaice.*
se Vee 128,600 flounder.
. 20. 1,896,000 7

38

April 20. 42,000 plaice.
3 20. 45, 000T ss. 15
4 23. 718,000 cod.*

a Ba: 462,000 haddock.*
- 23. 581,000 flounder.
“ 26. 561,000

May 1. 865,000
as 7. 1,447,000
rp 10. 530,400
ii WAL! 1SES1000%-4 12:
ss Paice 111,000

w

Total 14,144,400

During the autumn the hatching apparatus has been
thoroughly overhauled, and is now ready for use again.

A fresh stock of flounders (amounting to over 225 large
healthy fish) has been collected during the last three
months of 1900, so that part of the supply of eggs for
the season 1901 is practically secured. With the help of
the new steamer, and favourable weather, it is probable
that there will be a larger number of fry set free this
year than has yet been possible.

Description of an Apparatus for keeping Eggs wi motion.
(See Plate A.)

To successfully incubate large numbers of floating eggs
in the limited areas of the usual hatching tanks the water
must be kept in constant movement. When the eggs
are not disturbed they gravitate towards each other,
forming a layer on the surface of the water. Conse-
quently the result is a high mortality, chiefly due to
suffocation. It becomes necessary, therefore, to employ
some means to break up these masses. This is usually
done by slowly raising a weighted rod placed along the

o

BA

rows of boxes which allows the free ends of the boxes to
float up. ‘The rod is then suddenly released, and the
boxes depressed rapidly into the water, which is forced
up in powerful currents through the perforated bottom of
the boxes. This separates the eggs in all directions, but
without injury to the developing embryos.

The mechanism employed in other establishments
which use the same kind of hatching apparatus is driven
by a water wheel. This wheel turns a cam which has a
lever resting on itsrim. One end of the lever is weighted
to give the necessary pull to the wires that suspend the
rods. The other end has the main wires attached, and
from these branches are led over pulleys to the various
weighted rods. As the cam revolves the lever is alter-
nately raised and depressed so pulling up and then
releasing the wires.

The arrangement of the hatching apparatus at Piel does
not readily lend itself to the adoption of this method.
Some other system had, therefore, to ‘be planned, and
after various experiments, the apparatus now adopted by
us was devised. This apparatus has given complete satis-
faction during the last season, and as it is less compli-
cated than the older systems, a description and illustra-
tion may be useful to others, and will now be given.

The apparatus may be briefly described as a direct-
acting balance of the beam and scale pattern. It consists
in the main of a balanced beam (see Plate A, 5). One
end of the beam is attached to the middle of a light
framework, which carries the wires connected to the
weighted rods (5). The other end bears a frame contain-
ing a “tumbling” box (4) of a similar design to those
used in automatically measuring rainfall, washing photo-
graphic prints, flushing drains, &e. The box is so con-
structed that when empty it remains in a_ horizontal

35

position, but as it fills with water the centre of gravity
gradually alters until the box turns over and discharges
the contents, immediately returning to the horizontal
position again. The weight of the box and its frame
should just ‘be sufficient to raise the arm carrying the
frame with the wires, but without the weighted rods. The
quantity of water required to lift the rods and weights
is found ‘by weighing one rod with its weight, and then
multiplying that by the number of weighted rods
employed. The box should be made to contain rather
more than the exact quantity of water required. In the
Piel Hatchery the waste water from the apparatus and
other tanks is used for filling the box. When the box is
empty the rods are down and all the hatching boxes are
depressed. The box (4) gradually sinks to the floor as
the water pours in, pulling up the weighted rods (5). By
the time the rods are raised high enough (6 inches) the
box has lost its stability, and it falls over, discharging its
contents at once. ‘The rods at the same instant return
rapidly to rest, depressing the hatching boxes. The rate
of movement is easily controlled by regulating the flow
of water, and also by retarding or hastening the period
of instability of the tumbling box. ‘This latter can be
done by adding weights to the side of the box at B, or by
placing pieces of wood on the frame under the box at D.

The apparatus when fitted up can be attached to a beam
in the root of the room, and the whole should be so placed
that the framework carrying the wires attached to the

rods is vertically above the point of attachment.
Explanation of Plate A.
The drawing represents the front view of the apparatus,
1. Longitudinal beam resting on the cross beams

supporting the roof.

36

. Support for apparatus.
. Balanced beam.

Hm Co v9

. Tumbling box. At c a brass rod is rigidly fixed
working freely in hgnum vite ‘bearings fastened
to the frame. . aB=35} inches, ac=27} inches,
cb=9¥} inches, Bp=11 inches. Width=12 inches.

5. Wires to rods.

6. End view of hatching tanks, containing little

‘boxes for eggs.

i. Waste pipes leading into main pipe, taking water

to tumbling box.

8

End view of top and bottom of main suspender.

6 End view of suspenders of framework for wires and
tumbling box. The suspender to the tumbling
box works through a guide (gq).

¢ Side view of tumbling box in its frame.

NoTE ON THE SPAWNING OF THE MussEL (MyTILUS EDULIS),
By A. .Scorr:

The determination of the spawning period of the mussel
on the Lancashire coast has occupied our attention for
some time. Hitherto we have mainly examined the con-
dition of the reproductive organs, both im sitw in the
living animal, and by thin sections of prepared material
during periods of twelve months. Tow-nettings from the
vicinity of the beds have also been examined for the
larvee. These investigations enabled us, approximately,
to state when the eggs were shed. It is obvious, however,
that all the information regarding the actual spawning,
the fertilisation of the eggs, and the period that elapses
before the resulting embryos become free-swimming
larvee can only be ascertained by carefully observing the
living animal. It is not possible to do this under natural

or
md

conditions on the beds, and it becomes necessary to fall
back upon other methods which may not give altogether
conclusive results from a critically scientific point of view.
To remove animals from their natural surroundings and
place them in confinement in a limited area of water is
undoubtedly detrimental to life processes at first. After
some time the effects produced by the change may how-
ever be diminished, and the animals become acclimatised
and live probably very much as they would have done had
they been left in their original state. We are thus
enabled to carry on observations which would be quite
impossible under natural conditions.

Large samples, about + ewt., of mussels were collected
from the Roosebeck outer scar and from a scar in Barrow
Channel which only ebbs dry at low water of spring tides.
These were placed in the tanks in September, 1899, and
kept under observation for twelve months. <A constant
current of sea water was maintained, and from time to
time, usually twice a week, small quantities of mud, known
to contain diatoms, &c., were added to supply the animals
with food. The animals were examined microscopically
at intervals, and the reproductive organs compared with
samples taken direct from the beds.. The rate of develop-
ment was found to be practically the same in the mussels
in the tanks and in those on the beds.

On May 6th the mussels from both beds commenced to
discharge eggs. These were isolated and examined under
the microscope. No development took place. No ripe
males were found at this period, and it may be concluded
that these eggs were not fertilised. The mussels con-
tinued to discharge eggs which underwent no change until
June 14th. On June 13th the first obvious discharge of
spermatozoa occurred. This was from the mussels from
Barrow Channel, and so abundant was the supply that

38

the water in the tanks was rendered quite turbid, as if
milk had been poured in. A drop examined under the
microscope was found to be teeming with spermatozoa in
active movement. Two days afterwards the Roosebeck
mussels discharged spermatozoa. From that date on-
wards, although no further discharge of spermatozoa was
observed, the eggs were always fertilised. With a very
few exceptions the eggs were discharged during the night.
Many of the mussels were actually observed in the act
of shedding their eggs.

The embryos flow from the female in a slow distinct
stream. When not disturbed by currents they settle
down on the mud close to the parent as an obvious pink
mass. They remain in this position undergoing the early
stages of development, which last from eight to twelve
hours. They then rise to the surface as free swimming
larvee, and are dispersed by the currents. The duration
of the free swimming stage was not determined, but the
larvee remained free swimmers for at least four days.
The minute size of the larve (they are only from z¢3 to
zo Of an inch in diameter) prevents accurate observations
being made for one individual. They can only be kept
in jars where no circulation is going on, consequently the
surroundings soon become unfavourable to life. Attempts
to strain them through fine sieves, and so allow the foul
water to escape, were not a success, as the larve passed
through our finest sieves.

Fertilisation of the eggs has generally been thought to
take place in the water after they were discharged from
the parent. That has not been our experience at Piel.
After the obvious discharge of sperms all the eggs sub-
sequently extruded were found to ‘be fertilised, even
though no further discharge of spermatozoa could be
detected. In several instances the eggs were isolated as

BY

they were leaving the parent and put into water direct
from the sea that had been carefully filtered through fine
filter paper. These eggs always developed into free
swimming larve. Fertilisation therefore probably took
place in the branchial chamber of the parent.* It was
also observed that practically the whole of the reproduc-
tive elements were discharged at one emission extending
from one to three hours. The same mussel did not again
set free any more reproductive elements. When such a
spent mussel was opened up and examined the whole
reproductive organ was found to have collapsed.

The mussels on the beds, by the time those in the tanks
had ceased to emit reproductive elements and had become
quite thin, also took on the same appearance. From the
observations carried on at Piel the conclusion has been
arrived at that the spawning period of the mussels in the
northern part of our district may be set down as having
lasted this vear (1900) from the beginning of May to the

middle of July.

Report on THE Surimp TRAWLING Statistics CoLLECTED
BY Mr. G. Eccites on THE MERSEY SHRIMPING

(FROUND DURING THE PERIOD 1893—1899.

By Jas. Jounstone, B.Sc., and J. T. Jenxins, D.Sc.

In 1893 the Committee began a series of observations,

on the lines indicated in a scheme drawn up by Professor

* Professor M’Intosh some years ago investigated various points in the
reproduction of the mussel. Amongst other things, he determined that
the sperms were capable of living for twenty-four hours after being
removed from the parent. This has been confirmed by the work at Piel,
but the intervals between the obvious shedding of sperms and eggs in the
tanks were much longer than twenty-four hours, and during these periods
the sperms, even if alive, would be carried away in the waste water,

40

Herdman,* on the occurrence and distribution of the
commoner food fishes on the principal inshore and offshore
grounds of the Lancashire District. From time to time
selections from the results so obtained have been published
either in the Superintendent's Reports or in those of this
Laboratory. In the autumn of 1899 it was thought
advisable to make a study of all the data obtained, and as
a result all the forms (over 1,000) containing the records
of the observations have now been abstracted.

These observations were made by the Captain and crew
of the “John Fell” and by the bailiffs in charge of the
sub-districts, and are as complete as the police work and
other administrative duties of the officers permitted.
They include experimental hauls with fish-trawl] nets of
various sizes and made under various conditions, hauls
with shrimp trawls and shank nets, and observations on
the sizes, spawning, feeding, &e., of the common food
fishes. On account of the limited staff employed, the
extent of the district to be worked over and the pressure
of the police work, these statistics are necessarily very im-
perfect. It would be premature to publish many of the
data obtained, especially those of the fish-trawl, at
present, and we therefore confine ourselves to what seems
most complete and reliable, viz., the series of experimental
hauls with shrimp-trawl nets made by Mr. G. Eccles, head
bailiff for the Southern District, on the Mersey Shrimp-
ing Grounds.

It would not serve any useful purpose to publish the
results of these hauls as recorded ‘by Mr. Eccles in full,
so we have prepared an abstract of all the data collected
and present it in the form of Tables I. to VI. Altogether

248 hauls with a shrimp trawl were made during the ~

period 1893-1899. By far the greatest number of these
* Lancashire Sea Fisheries Laboratory Report for 1892, pp. 41-45,

1]

were made from the New Brighton sailing boat. A few
were made by the “John Fell,” and are included amongst
the others. The conditions under which the hauls were
made were not strictly uniform. As a very general rule
a shrimp trawl of 21 feet beam and 33 feet length of net,
with a mesh measuring half an inch from knot to knot,
was employed. Very occasionally a slightly longer beam
(24 feet) has been used. The greater number of the drags
made were two miles in length and one hour in duration,
and these conditions were adhered to as closely as cireum-
stances permitted. Occasionally, however, the length and
duration of the drags were greater, more often less, than
the values stated, and from this cause individual hauls
are, strictly speaking, not comparable with each other.
In the treatment of the data it has, therefore, been
thought advisable to make the average hauls per month
the values compared, and as the averages of a number of
hauls have generally been used in whatever comparisons
we make, to that extent the error due to fishing under
shghtly inconstant conditions has, we consider, been
eliminated.

The recorded results of these hauls include (1) the total
numbers of edible fish caught, (2) the numbers of quarts*
of shrimps taken, (3) the numbers of the various species
of food fishes with (generally) their average sizes, (4) state
of weather, sea, wind, &c., (5) physical observations. The
commoner fishes taken are:—The sole (Salea vulgaris),
the plaice (Plewronectes platessa), the dab (Pleuronectes
limanda), the haddock (Gadus eglefinus), the whiting

* We employ the quart of shrimps (the economic unit) as the measure
of the catch. A quart contains a variable number of shrimps, 200 to 400,
the variation being due to the varying sizes of the animals. The market
value varies from 6d. to 8d., that is the price paid by the consumer ; the
fisherman himself receives only about 3d. per quart on the average if he
sells his catch to the fishmongers. But a considerable proportion of the
shrimps caught (about one-third) are retailed by the fishermen themselves,

{2

(Gadus merlangus), the cod (Gadus morrhua), and the
herring (Clupea harengus). Less commonly the lemon sole
(Pleuronectes microcephalus), the brill (Rhombus levis), and
the gurnard (T'rigla gurnardus) are taken. Various inedible
fishes are frequently caught, the commoner of which are
Solea lutea, Trachinus, Cottus, Centronotus, Ammodytes, and
with every haul a great number of invertebrates are taken.
Often the crabs (Portunus) brought up form half the bulk
of the catch. Starfishes (Asterias) are nearly always

caught. In the warmer months large meduse are
abundant.

We quote a few individual hauls in detail as samples.
I.—August 28th, 1895. Near Deposit Buoy (see chart

on p. 46), in 5 fathoms of water, bottom of sand
]

and mud. Length of drag = 2 miles, duration
=70 minutes. Shrimp trawl of 21 feet beam.

Sole... 48, length — 43 inches mostly, but 16

were over 4oz. in weight.

Pisce, 16205" 6 inches.

Dab ees: G04" 6a

Whiting 757, ., Gan 1B}

Cod). (Sone 3, a ere

Gurnard 30" =.) ANTE oe

aye Gas nee S, 7,4, broad across pec-

—— toral fins.
Total food fishes 3144. Shrimps, 27 quarts.

II.—September 27th, 1893, near Deposit Buoy, in
5 fathoms of water; bottom of sand. Length of
drag = 2 miles, duration = 90 minutes. Shrimp
trawl of 21 feet beam. ‘Twenty boats were
fishing immediately around.

Sole .... 12, leneth — 44 inches.

Plaice 10407, 2 ery,

15

Dab... +875, length = 4 inches.
Whiting 169, 4 5
Cod shee Ry (GO ¢ 5 ‘

Total food fishes 110382. Shrimps, 82 quarts.

The soles and plaice taken in this haul are
deseribed as “deadly,” dabs, whiting and cod
aa lavely.’”

[1l.—August 50th, 1899, near Deposit Buoy, in
6 fathoms of water; bottom of mud and sand.
Length of drag=2 miles, duration=one hour.
21 feet shrimp trawl.

Sole... 257, 11 were over 8 inches long, 4 of the
catch were over 2 and under 8 inches,
the remainder were 2 inches lone.

Plaice... 265, 6 were over 8 inches long, the re-
mainder were 2 to 4 inches in length.

Dab ... 896, 2 were over 8 inches long, + of the
catch were about 2 inches, the re-
mainder 13 inches long.

Ray ... 18, 7 inches broad.

Whiting 285, 5 inches.

Total food fishes 1721. Shrimps, 20 quarts.

IV.—Mareh 15th, 1895, in Crosby Channel (see chart),
in + fathoms of water. Bottom of sand. Length
of drag=1 mile, duration=30 minutes. Shrimp

trawl 24 feet beam.

Flounders ... 2, leneth = 4 inches.
Cod Shine 10, x3 if 9
Total food fishes 12. No shrimps were caught,

Ad

IT. is one of the largest hauls made on the ground.
TV. is one of the smallest. It will be seen later, however,
that the hauls made on the ground dealt with in II. differ
considerably from those made near the Deposit Buoy.

The actual data considered here are given on Tables I.
and II. Of the various species of edible fish enumerated
above only 4 are dealt with—the sole, plaice, dab, and
whiting. Consequently the totals under the heading
“Total numbers of fish” are not the sums of the numbers
representing the catches of the four fishes mentioned.
Those sums are less than the totals by the numbers of fish
of various kinds which are not tabulated. For each of
the years 1895-99 the tables give (1) the number of hauls
made during each month, (2) the total number of fish
caught in all the hauls and the average number of fish
caught per haul, (3) the total number of quarts of shrimps
caught in all the hauls and the average catch per haul,
(4) the total number of each of the four kinds of fishes
caught in all the hauls and the average numbers caught
per haul.

Table T. deals with the observations made on a portion
only of the whole Mersey shrimping ground. Most of the
hauls have been made within two miles of the Deposit
Buoy, that is on the shallow water immediately behind
Burbo Bank. A few were made in a small portion of the
Rock Channel (see Chart, p. 46).

Table II. gives the hauls made in the deeper water of
the Channels—part of Rock Channel, Horse Channel,
Queen’s and Crosby Channels. The division of the whole
ground into these two sub-divisions is not quite natural
since all the Rock Channel ought, strictly speaking, to
have been dealt with in Table If. But it was found
convenient for various reasons to include the eastern
portion of Rock Channel in Table |

45

It will be seen that there is no complete series of
observations, including at least one haul in each month of
the year in either Table I. or If. On this account and
also with the object of eliminating as far as possible
accidental conditions and variations, all the hauls taken
during the Januarys in each of the years 1893-99 have
been collected, and from these the total fish and shrimps
caught and the averages per haul have been calculated.
The same has been done for the other months, and the
results are tabulated in Tables II]. and IV. III. deals
with the portion of the ground considered in ‘lable I., and
IV. with the portion considered in Table Ll. In Table
VI. all the fish caught in the third quarters (July, August,
September) of each of the years 1895-9 are collected, the
numbers of hauls taken in each of those quarterly periods
are given, and the average catches are calculated. In
Table V. an attempt is made to compare the varying
destruction of young fishes at different times and on the
different grounds.

We give on next page a map of the Mersey Shrimping
Ground which has been reduced from the Liverpool Dock
Board’s Chart of the area. It represents the extent of the
sandbanks at low water of a spring tide ten feet below the
level of the Old Dock Sill Datum at Liverpool. Almost
the whole of the area shown is regularly fished over.
More exactly, a line drawn from the N.W. extremity of
Kast Hoyle Bank to Neweome Knoll Buoy, and from
Newcome Knoll Buoy to the first red conical buoy in
Queen’s Channel, defines the seaward limit of the Burbo
Bank area. Shrimping is carried on over almost all this
ground, the extent of which is roughly 16 to 18 square
miles. Queen’s Channel, lormby Channel, Crosby
Channel, Horse Channel, and the western portion of Rock

Channel are also regularly fished. Shrimping is also

46

earried on in the gutters through the banks, and when
there is sufficient water on the margins of the banks
themselves. A portion of this area, about 4+ square miles
in extent, lying between Newcome Knoll and Deposit

=e \/ | ; 5
fy

~

ROCK CHANNEL
pn Re

MOCKBEGGAR Ww HARE

Mmrsry SHRIMPING GROUNDS.

Buoys and to the north of these, has a bottom of fine mud,
which to some extent hinders the working of shank nets.
Over almost all the rest of the area the bottom consists of
fine sand. Shrimp fishing, however, is not confined to
this area. .A considerable area to the north of Queen’s

A7

Channel and a portion of the Mersey estuary lying above
the Liverpool Landing Stage are also fished on.

Now with regard to the relative quantities of shrimps
and immature fishes caught in the shrimp trawl, con-
siderable differences exist on different parts of the whole
area referred to above. We have, therefore, separated the
hauls taken on the portion lying seaward from Burbo
Bank and south of Queen’s Channel from the portion
including Queen’s, Formby, Crosby and Horse Channels,
and the eastern part of Rock Channel. For convenience
the former portion will be referred to hereafter as Area A
and the latter as Area B. The hauls taken on Area A
are abstracted in Table I., those taken on Area B on
Table II.

In Plate B we have represented graphically the results
of Tables III. and IV. The method adopted has been
to take each fish separately, and to superpose the curves
representing its distribution on the two sub-divisions of
the shrimping ground referred to above. Curves L., IL.,
IIl., IV., and V. represent the variation from month to
month in the numbers of immature whiting, plaice, dabs,
soles and shrimps taken per average haul. In all these
curves the number plotted along the vertical axes repre-
sent these average hauls; months are represented on the
horizontal axes. The vertical seale of L., I1., and III. is
the same; the corresponding scale of IV. is one-tenth, and
\. one-twentieth that of I. This change of scale has beea
necessary on account of the small values dealt with in
IV. and V. In all the curves the thick line represents
the average hauls on Area A, the thin line the average
hauls on Area B. It ought to be remembered that the
fishes dealt with in these tables and curves are nearly al!
immature. The hauls quoted on pp. 42-5 represent fairly
their average sizes.

48

In the case of the whiting (I.), the maximum catch
(1,180) has been taken in August. This is the case on
both areas, and it is the case also for Area A in 1893,
1894, 1895, and 1899. In 1896 the maximum catch was
taken in July, in 1897 and 1898 in September. The series
for individual years are not so complete for Area B, and
it is to be noted that in 1895 the catches increase during
the latter half of the year to a maximum in November.
The catches of whiting during the third quarter of the
year were greater in 1895 than in any other year of the
period under consideration. In both areas very low
catches were made in June, and after this month the
curve rapidly rises towards the maximum in August. A
secondary maximum (on both areas) occurs during April.
It is remarkable that the form of the curve is the same
for ‘both areas, the maxima and minima occurring at the
same time. he curve also shows that throughout the
year greater catches were always taken on Area A, and
that between June and November the catches there were
very much greater than on Area B.

In the case of plaice (I1.) the maximum catch was
made on Area A in September. This is also true for the
three years, 1895, 4, and 5, having the most complete
series of observations. ‘he minimum occurs at the end
of the year. It is generally the case in the individual
years that the lowest catches were made at the beginning
or end of the year. As in the case of whiting, a
secondary maximum occurs during the spring.

The form of the curves for plaice difters completely for
the two areas. In B there are three maxima, January,
July and November, and two minima, May and August.
Generally it would appear that plaice are more abundant
in the Channels during the winter months, that during

the late winter and spring their number decreases, and

49

increases again toward midsummer. After midsummer
they become less abundant, but during the autumn and
early winter they increase again. ‘That is to say, that
except for the increase towards midsummer, which is
characteristic for both grounds, and is largely due to the
appearance of fish of that same vear’s spawning, their
distribution on the two areas is to some extent comple-
mentary. The general conclusion is confirmed by the
study of the figures for the separate years (as far as these
go). This curious behaviour of the same fish on two
adjacent areas is perhaps to be explained by supposing
that migration from the one area to the other takes place
during the spring and autumn. What the causes of such
migration may be we are not in a position to say. The
migrating fish are largely those of that same year’s
spawning.

It might be expected that the distribution of dabs
would follow closely that of plaice. It will be seen that
the curve of distribution (III.) on Area A is very similar
to that for plaice. The minimum for both fishes occurs
at the beginning or end of the year, but the maximum
catch was taken earlier in the year in the case of the dab.
In the three years, 1895, 4, and 5, for which the data
are most complete, the maximum catches of dabs were
made earlier than those of plaice. As in the case of
whiting the curve shows two maxima which have the same
positions.

The distribution of dabs on Area B is not exactly
similar to that of plaice, but seems to be rather irregular.
It is, however, the case that large catches were made there
at the beginning and end of the year. The catches made
about the middle of the year are, however, somewhat
irregular.

D

50

Soles (IV.) have much the same distribution on Area
A as the other fishes dealt with. The maximum catch
was made in August. The secondary maximum occurs in
March, a month earlier than that of dabs and whiting.
The minimum catch was made at the end of the year.
Three hauls were made on this ground during December,
in none of which were soles caught. The distribution on
Area B is more irregular, and no general statement can
be made with regard to it.

Shrimps (V.) have been caught at any time during the
year on both areas, except in one exceptional haul
(quoted on p. 45). It is to be noted that their distribution
differs somewhat from that of the food fishes; the mini-
mum catches were made (on both areas) in February.
From then the average catch rises with small variations
to the maximum in October. During August, September
and October the catches do not vary much, rising very
slowly. After October they fall very rapidly.

A study of the curves representing the monthly varia-
tion of shrimps on the two areas shows this remarkable
condition: from December till the following August
shrimps are always more abundant on Area A than on
Area B; conversely from August to November they are
more abundant on Area B than on Area A. That is to
say, during the four months, August to November,
shrimps are more abundant in the channels than on the
banks. . We think it necessary, however, to state that
this may be due to the fact that most of the fishing is
carried on during these four months on Area A.

Since all shrimp fishing, whether on Area A or B, is
necessarily attended by the capture of a variable number
of immature fish, we have thought it useful, in view of
the practical importance of this fact, to study the varia-
tion in the relative quantities of shrimps and fish caught

51

in the shrimp trawl. If the number of fish caught in
any one haul be divided by the numbers of quarts of
shrimps taken at the same time, a measure is obtained of
the amount of destruction of young fishes caused by
shrimp trawling. Taking the total monthly catches of
shrimps and fish during the year, as shown in Tables III.
and IV., as a basis, we have constructed Table V. That
table shows for each month in the year, and for both
areas, how many soles, plaice and whiting were caught
for every quart of shrimps. And if it be possible to
determine by any means the total number of quarts of
shrimps landed from the Mersey Shrimping Grounds in
each month during the year, the numbers on this table
will serve as factors which will enable the amount of
destruction of immature food fishes to be calculated.

The numbers of plaice caught per quart of shrimps on
Area B during February and March seem excessive. This
is due first to the relatively large numbers of plaice found
on that ground during the early months of the year;
second, to the very small catches of shrimps made there
during those months.

The tables show that the numbers of soles, plaice and
whiting caught per quart of shrimps on Area A is always
much greater during the third quarter of the year than
on Area B during the same period. More exactly, more
whiting are caught on Area A from June to December,
and more plaice and soles from August to October, than
on Area B during those same months. More whiting
were caught on Area B than on A during February, and
more soles during March, May, June, July, November
and December.

We have used the term destruction as synonymous with
capture of young fish, but perhaps we are not strictly
justified in doing so. All the fish brought up in a shrimp

a9)

re)

trawl do not necessarily die. It will be seen by reference
to the hauls quoted on pp. 42-3 that a few large fish are
generally taken. These are always alive when brought
up from a drag of moderate duration, and if immediately
thrown back into the sea will most probably survive. We
refer to plaice, soles and dabs over 8 inches in length.
Flat fish from 5 to 8 inches are not so hardy, but many of
these are alive when the “net is fished,’ and probably
recover when put back into the sea. The vitality experi-
ments made by Mr. Dawson* and others in our district
have shown that quite a large proportion of such fish
recover when taken from the contents of the net and
immediately put into a tub containing running sea water.
But the flat fish under 5 inches long are im a worse case,
and the greater number of these are probably really
destroyed. They are small, and in the process of “ sorting
the catch,” all the larger animals (large fish, crabs, star-
fish) are thrown overboard first, so that small flat fishes
have to lie on the deck for a longer period than the others.
Small round fish, whiting, haddock and cod of less than
5 inches long are almost always dead when the contents of
the net are emptied on the deck. The larger round fishes
may be alive, but they seem to be less hardy than the flat
fishes.

Of course the mortality among the fishes caught in the
shrimp trawl must depend to a very great extent on the
care of the fishermen in sorting the catch, on the facility
with which the net can be hauled, on the duration of the
drag, and on the temperature ; in warm weather the water
adhering to the gills is more easily evaporated and
contains less dissolyed air. It is to the interest of
the fishermen to sort the catch quickly, and get the

* Lancashire Sea Fisheries Laboratory Reports for 1898, (p. 23) and
1894, (p. 30).

i

= 6>
yey

shrimps put aside, and we believe that they really wish to
preserve the life of as many of the immature fish caught
(which are not marketable, and are of no use to them) as
possible. And we have seen that the contents of the net
ean be very rapidly sorted out. But in a large catch the
process is somewhat tedious, and as the deck space in a
shrimping boat is very limited, part of the catch may be
put into fish ‘baskets wnsorted, while the remainder is
being dealt with. In these circumstances the immature
fish in the reserved portion have little chance of life.

It is clear that with long drags, with large catches, and
in warm weather the mortality among the immature fish
taken in the trawl is much greater. Considering all
things, there is not much doubt that of the immature fish
taken in the course of shrimp trawling, as at present
carried on, a large proportion must necessarily be
destroyed.

We have made an attempt to determine the distribu-
tion from year to year of the four fishes considered above.
The average hauls for each fish for the third quarters of
each of the years 1895-9 have been calculated, and these
are the values compared. ‘The third quarters (July,
August, September) are selected since those are the
periods during which the greater number of hauls were
made, and because they contain the maximum catches for
all the years and fishes considered. The values dealt
with, therefore, are those representing most probably the
condition of the fishery in each year. The results are
tabulated in Table VI., and they are represented graphi-
cally in the corresponding set of curves (VI.) on Plate C.

During this period the average catches of plaice have
decreased from the maximum catch (2,045) in 1893 to the
minimum (176) in 1899. The decrease from 1893 to
1894 was very great. From 1895 to 1897 the catches were

ot

nearly constant, dropping again in 1898. The maximum
catch of dabs was made in 1894; from 1894 to 1897 the
catches of dabs steadily declined, recovering again in
1898. The maximum catch of whiting was made in 1896,
and the catches then decreased till 1897, when they again
began to increase. It is singular that the maximum
catches of these three fishes, plaice, dabs, and whiting,
are observed in three consecutive years.

The catches of soles, on the contrary, show a nearly
regular increase during those seven years. The minimum
catch was made in 1894, the maximum in 1898. The
decrease from 1898 to 1899 is very slight. We have
evidence that a similar, though greater, increase in soles
has taken place on the Blackpool closed ground.

No deduction as to the effect of fishing on the distribu-
tion of these fishes during the period considered can, of
course, be made. The period is too short and the varia-
tions observed are too great. There can be little doubt
but that the fluctuations are due in the main to the
operation of natural causes.

We must insist on the inadequacy of these statistics to
a thorough understanding of the causes influencing the
distribution, on different areas and at different times, of
the fish population of the Mersey shrimping grounds.
So far as they go they are valuable, and they do give some
information regarding the seasonal variation and the
relation to each other of the various forms considered.
But they suggest many more problems than they aid us
in answering. The increase in the catches of soles on the
Blackpool and Mersey grounds is an instance. This
happening on two grounds, one preserved against, the
other open to, shrimp trawling, is remarkable. A satis-
factory answer might have been given by a much more
complete series of observations than we possess, which

~
~

might have enabled us, from a consideration of the
relative increments in the catches from year to year, to
have connected the increase on the Blackpool ground with
its closure against the destruction of immature soles by
shrimp trawling. But comparatively few hauls have been
made on the Blackpool ground, and the opportunity has
been lost.

No regular observations regarding the distribution of
the plankton or of the bottom invertebrate fauna of the
Mersey ground have been made, and we have therefore no
material for a possible explanation of the fluctuation in
the fish fauna outlined above. It is particularly un-
fortunate that regular and exact physical determinations
of temperature, specific gravity, salinity, &c., were not
made during the last eight years. These must be
essential portions of any future investigation of this area.*
The nature of the sea bottom is very peculiar, and a com-
plete investigation of this is to be desired.

We believe that observations on this ground, with a
view to the regulation of the fishing, will be unsatis-
factory unless accompanied by enquiries into the relations
of its fish population with the spawning fish on the off-
shore grounds on the one hand, and with the larger
immature fish population of the offshore grounds on the
other. Such investigation and enquiries into the stability
of the immature fish population of the shrimping ground

are very relevant.

* See scheme given in this Report, p. 24.

REPORT ON THE DEPOSITS FROM THE LIVERPOOL

‘“ Hoprers”’ IN RELATION TO SHRIMPS AND YounG FIsH.
By W. A. Herpmay.

Early in the year the General Purposes Committee
asked for a report on the eftect produced upon the move-
ments of shrimps and young fishes by the materials carried
out to sea from Liverpool in the hopper barges and
deposited near the Burbo Bank. It had, I believe, been
suggested (1) that the shrimps were attracted to this
particular ground—where young fishes are also found in
great abundance—to feed upon the refuse in the deposits ;
and (2) that if the attractive material were deposited on
some other neighbouring ground not frequented by small
fish the shrimps would follow, thus leading to such a
separation of shrimps from young fish on the bottom as
would admit of shrimping being carried on freely without
causing any destruction of young fish. It would certainly
be very convenient if it were so, but a careful examination
of the facts shows that there is no real foundation for the
ingenious suggestion.

Mr. Dawson, after discussing the matter with me,
caused the necessary samples and specimens to be
obtained from chosen localities in the area in question,
and these were sent to the laboratory where Mr. Johnstone
and I carefully examined them, and drew up the follow-
ing report for the Committee : —

“Report by Dr. Herdman on Deposits, Shrimps,
and Young Fish.

* A number of samples have been obtained during the
last two weeks by Mr. G. Eccles, and were brought by him
to the Laboratory for examination.

C
=~]

These represent : —

ies

5O

Samples of the sea bottom at and about the
* Deposit buoy.” (See map on page 46).

. Samples of the sea bottom near the Rock Channel

(No. 7 buoy).

. Samples of the deposit found in gutters on the

edge of the Burbo Bank at low tide.

. Material taken from a ‘ Hopper” in the Man-

chester Ship Canal.

. Samples of shrimps caught near the Deposit buoy.
. Samples of young flat fish caught near the

Deposit buoy.

“These have all been carefully examined in the Sea-

Fisheries Laboratory, and microscope preparations of the

various substances have been made and compared.

The examination has shown : —

be.

20

4°.

That there is comparatively little fine mud or
dirty material at the Deposit buoy. The
bottom appears to consist largely of coarse
crystalline sand.

. At No. 7 buoy the deposit is dirtier, and has

more mud and amorphous decomposing
material.

In the gutters at low tide the deposit is also
dirtier than at the Deposit buoy, and more
like the refuse from the Hoppers.

The material from the Hopper was very dark
coloured, and had much more yellow and black
amorphous decomposing stuff than is found on

the sea bottom at or near the Deposit buoy.

. The shrimps caught about the Deposit buoy con-

tained in the stomachs—sand, vegetable tissue,

animal debris, legs, &c., of small Crustaceans,

58

Foraminifera, Annelid sete, along with a
certain amount of sand.

6°. The stomachs and intestines of the young fish
(mainly dabs) brought to the Laboratory from
near the Deposit buoy were full of sand, with
fragments of shells and remains of animals.

‘“ ConcLustons.—So far as these samples show, there is
no reason to think that either the shrimps or the young
fish feed upon the stuff deposited by the Hoppers. They
did not show any traces of it in their stomachs, nor are
they specially abundant where the bottom shows the
greatest amount of dirt and decomposable material.”

* University College, “W. A. HERDMAN.”
“ March 15th, 1900.”

Mr. Dawson and I therefore agree that it is a mistake
to suppose (1) that the Liverpool refuse is especially
abundant at the bottom in the neighbourhood of the so-
called “deposit” buoy, which is on the Burbo Bank
Shrimping Ground, and (2) that shrimps feed specially
upon such refuse. Consequently the idea that the shrimps
are attracted to the ground they frequent by the Liverpool
deposits may be relinquished, and it is very improbable
that changing the place of deposition would have any
favourable effect upon the present distribution of shrimps
and young fish.

As a matter of fact, as Mr. Dawson has pointed out in
one of his quarterly reports, the steam hopper barges con-
veying the refuse generally go much further out to sea
than the area in question before discharging; and, with
the exception of sand, no material of any kind has
apparently been deposited in the neighbourhood of the
deposit buoy and from there to the Burbo Bank for some

time.

59

It is probable that the conditions in these shallow
sandy channels which suit the shrimps are also the most
suitable conditions for young fish—especially flat fish—
in certain stages of growth, and consequently it is futile
to hope that any artificial operations will lead to the
separation of the two kinds of animals.

NorE oN A SPoROZOON PARASITE OF THE PLAIcr.
(PLEURONECTES PLATESSA).
By James JOHNSTONE.
(With Plate D.)

Two specimens of plaice have come to the Fisheries
Laboratory during the year which showed a_ peculiar
modification of the intestinal wall. One specimen was
sent by Mr. G. Kecles, Chief Fishery Officer at New
Brighton. It was caught near the Mersey Bar at the
beginning of October. The other was sent to me by Mr.
A. Scott. It had been caught by Mr. Wright, Fishery
Officer, in Barrow Channel, on October Ist, 1900.

The first specimen was a female about 8 inches long.
Ti had been opened, and the head cut partly off. Mr.
Kecles was struck by the granular appearance of the
viscera, suggesting the presence of a large quantity of
spawn. As however the fish was much too small to con-
tain ripe ovaries, he thought it worth sending to the
Laboratory. It was fresh when it came to hand, and the
fish looked in good enough condition. ‘The ovaries were
about one inch in length but perfectly normal for a fish
of this size. The intestine, liver, kidney, &c., had their
usual relations.

But the greater portion of the intestine, from the
pylorus to about 13 inches from the anus was thickened,
and had the appearance of a ripe ovary. ‘That is, the
surface was studded with little round white opaque bodies

60

lying close together, and shining through the peritoneum.
The fresh intestine was precisely similar to that of the
second specimen, which is represented in Plate D, fig. 1.
On cutting open a portion of the gut it was seen to have a
much reduced lumen. The wall was 3 or 4 mm. thick.
Its internal surface was thrown into close set and deep
longitudinal folds pursuing a zigzag course. All the
surface of these showed the same round white bodies pro-
jecting from their surfaces.

The stomach was normal in form and relations except
that its walls seemed thinner than usual. No food con-
tents were present. In the modified portion of the intes-
tine there were traces of decomposed food matter. A few
fragments of Lamellibranch shells were found, and were
identified as young Donaa vittatus.

The second specimen, sent by Mr. Scott, was the
intestine of a female plaice 11 inches long. It had been
preserved in corrosive-acetic fixative before reaching here.
From Mr. Scott's description the fish seems to have been
quite normal in other respects. The ovaries were of
normal size and relationships.

Almost the entire post-pyloric portion of the intestine
in this specimen was modified in precisely the same way
as in the other case described above. Fig. 1 represents a
portion of the intestine of this fish. ‘The maximum
diameter was about 1 inch. This thickest portion lay
immediately behind the stomach. The pyloric caeca could
be recognised, but were greatly flattened out. Near the
anus the inclusions in the wall became fewer, and a small
portion was free from them. No traces of food matter
could be recognised in the lumen.

Pieces of both intestines were hardened in alcohol,
embedded in paraftin, and sections were made. Fig. 2
represents a small portion of the wall of the first specimen

61

cut in transverse section. No mucous membrane is
recognisable, and the whole wall is filled up with roundish
bodies, each of which appears on examination with a
moderately low power to be filled up with a homogeneous
material. These bodies are closely packed together, and
between them lie a few connective tissue fibres. Some
masses of disintegrated tissue lay between the folds which
may possibly have represented the disintegrated mucosa.
Fig. 3 represents a small portion of the same section under
a much higher magnification. Outside of all may be seen
a layer of peritoneum (/’e7.) and internal to this is a thin
longitudinal layer of plain muscle fibre (J//.). Within
this layer of longitudinal muscle fibres is a layer of
eireular fibres (J/.¢.), also unstriated and about three
times the thickness of the former layer. Within this,
again is a layer of loose areolar tissue (S. muc.) from which
fibres pass through the thickness of the wall of the
intestine between the spherical bodies.

The arrangement of the muscle layer is therefore
normal, and the foreign structures lie in the sub-mucosa.
Of the mucosa itself there is no definite trace. A delicate
sheet of connective tissue covers the free surface of the
folds. This is easily torn, and the little spherical bodies
can be readily dissociated. ‘They are perfectly spherical
in the fresh state, and have an average diameter of about
0G mm. The structure of a portion of one of these cysts
is shown in Fig. 5. There is a capsule (C.c.), consisting
of an outer cuticular layer and an inner irregular layer,
which is fibrous in appearance, and apparently contains no
nuclei. Within this capsule the cyst is filled up by a
vast number of minute spore-like bodies. These are oval
in shape. They have a maximum diameter of about 5 #.
They do not stain, and present no obvious internal
structure.

62

It is obvious from the above description that we have
to deal here with a Protozoon parasite, most probably a
Sporozoon form. Possibly it is one of the Gregarinida,
but at present I am unable to determine the genus.

Explanation of Plate D.

Fig. 1.—A small portion of the gut of the second

specimen. Natural size.

Fig. 2.—Part of a transverse section of the wall of
the gut of the first specimen.
x 15 diameters. / internal, # external,
surface.

Fig. 3.—Part of the same transverse section; x 390
diameters. Per. peritoneum; J//, longi-
tudinal muscle layer; dc, circular muscle
layer; S.muc, sub-mucosa; Cc, capsule of
a cyst; Sp, spore contents of the cyst.

Fig. 4.Several spores from the first specimen
x 2,500 diameters.

63

On THE FisH Parasites, LeEPEOPHTHELRUS AND LERN@&A.
By ANDREW Scort,
Resident Fisheries Assistant at the Piel Hatchery.
(With five Plates.)
INTRODUCTION.

There are comparatively few fishes that do not, at some
period of their life history, prove on careful examination
to be the host of at least one kind of parasite, either crus-
tacean or worm. ‘The worm parasites are usually found
infesting the alimentary canal (Nematodes and Cestodes),
the gills and skin (Trematodes and Bdellodes), while
Crustacean (Copepod) parasites are almost entirely con-
fined to places in direct communication with the exterior,
such as the skin itself, the fins, the mouth, the branchial
chamber, attached to the gills and operculum, in the
nostrils, and in the mucous canals. ‘They may even be
found attached to the eye, as Lernwenicus spratte in the
sprat (Clupea sprattus); and Lerneopoda elongata in the
Greenland Shark* (Acanthorhinus carcharias), causing in
the latter at any rate partial blindness; or burrowing into
the abdominal cavity, as Penella évoceti in the flying
fisht (Hvocetus volitans), till only the ends of the ovisacs
are visible from the exterior.

The Copepod fish parasites have attracted much atten-
tion from Zoologists for a very long period, since the time
when Aristotle, in his * Historia Animalium,” tells us
that the tunny and the sword fish are tormented by a sort
of worm which fastens itself under the fin. Many of

* Mr. R. L. Ascroft, of Lytham, who visited Iceland on a ‘‘ steam liner,”
fishing for halibut, &c., a year or two ago, says nearly all the sharks caught
on the lines had these parasites in their eyes.

+ One was exhibited at a meeting of the Liverpool Biol. Soc. in 1897,
infested by two such parasites, recorded as P. blainvilli, which in turn
were covered with a number of small Cirripedes.—Trans. L’pool Biol. Soc.,
vol. xi,, p. Xil.

64

the parasites now known to be Copepods were not at
first recognised as Crustacea, chiefly because of the diffi-
culty of making out the true characters and the absence
of knowledge as to the life-histories. There was much
difference of opinion even as to which were really the
anterior and posterior extremities of these animals, due
to the fact that the posteriorly placed ovisacs of the then
known forms are cylindrical tubes which were by some
supposed to be the antennules, and therefore that end
was called the anterior. Hence many of the drawings of
the earlier authors represent the animals standing on their
heads.

Baird’s “ British Entomostraca,” published by the
Ray Society in 1850, marks an important epoch in our
knowledge. This author gives an interesting historical
account of the group, brings together all that was pre-
viously known, and gives a very full account, with
excellent figures, of all the British species known at
that time, and although some of these are inaccurate in
detail, or have been added to by more recent investiga-
tions, still Baird’s monograph is indispensable to any one
working at the subject. Since 1850 comparatively little
has been done in this country to increase our knowledge
regarding the distribution or habits of these crustaceans.
Within the past few years, however, the study has revived
and some important papers, mainly speciographic, have
been published.

The latest classification of the Copepod fish parasites
arranges them under seven families, as follows :—Ereast-
LIDH, CaLicipm, DicHeLEstipm, Parinicntayip®, LERNIDA,
CHONDRACANTHIDEH, and Lernmopopipm. With the excep-
tion of the Puimicurnuyipm, all these families have
representatives living on fishes found in the seas around
our coasts.

65

These parasites vary considerably in size, ranging from
one-thirtieth of an inch to nearly two inches in length.
They also differ very much in shape. Some have their
locomotor organs well developed, and are capable when
necessary of leading a pelagic life for a period. Others
have lost all swimming power, and become mere inert
sacs, securely attached to their host by anchor processes,
embedded in the tissues, and when. taken off their host
they soon die from want of food and oxygen.

The sexes are separate, the males as a rule being much
smaller than the females. In many cases the males are
practically parasitic on the females, especially those of the
Chondracanthide and Lerneopodide. The fact that the
males are found upon egg-bearing females of the above
families is due to their power of locomotion having been
lost when they reached maturity. When once they have
settled down and matured they are unable to change their
position to any extent. Fertilisation of the female is
effected early in its life history, before the metamorphosis
is completed. One copulation, apparently, is all that is
necessary to fertilise the female for hfe. The resulting
embryos remain attached to the external opening of the
oviduets, either in a single or multiserial column, enclosed

in a sac, until they hatch. The period of incubation
extends over several weeks. The young parasites hatch
out as nauplii, with three pairs of appendages. The

nauplii undergo metamorphosis, which in some forms
after a certain stage is reached is retrogressive, finally
leading to the adult condition.

The Copepod fish parasites are generally regarded as
being composed of about sixteen somites. Usually, how-
ever, some of these somites are suppressed or fused
together, forming one compound segment, the true
character of which is rendered evident by the appendages

b

66

attached to it, each pair indicating a somite. At one end
of the series, these parasites approach very nearly in
structure and general appearance to the non-parasitic
Copepods. At the other end they are extremely different,
exhibiting most remarkable examples of retrograde
development, and without a complete study of their life
history it would be quite impossible to recognise them
even as Crustacea.

In the following pages an account is given of the
anatomy and metamorphosis of one member from each of
the two very different families, the Caligide and the
Lerneide, the forms chosen being Lepeophthewrus
pectoralis and Lernea branchialis.

The Caligide is the most extensive family of the Cope-
pod fish parasites, and contains a larger number of genera
and species than any of the others. As it stands at
present, there are 124 species representing 25 genera.
Three-fifths of the known species of Caligide belong to
two genera, Caligus and Lepeophtheirus. Some earlier
authors have not recognised the latter genus, and include
the various species belonging to it in Caligus. There are,
however, very important differences between the two
which make their appearance early in life. These
differences are constant, and give good cause for establish-
ing a separate genus. Caligus has two semicircular
suckers on the frontal margin of the cephalic shield, which
are developed before the “ chalimus’’* stage is completed,
and the biting part of the second maxille has only one
tooth. In Lepeophtheirus these suckers are entirely absent
all through life, and the biting part of the second maxille
has two teeth. The changes that take place between the
‘“nauplius” stage, when the animal is hatched from the

* The stage at which the animal first becomes attached to its host. —
(see p. 94).

67

egg, and the adult condition are practically the same in
the two genera, and probably also in the other members
of this family. From investigations carried on during
the past two years, it may reasonably be concluded that
Lepeophtheirus, throughout the remainder of its life and
under normal conditions remains on the same fish that it
attached itself to at the beginning of the “ chalimus ”
stage. It is very rarely met with in tow-net collections.
On the other hand, Caligus does not always remain on the
same fish. At the completion of its ‘chalimus”’ stage it
frequently leaves its host, and for a time leads a pelagic
life. Tow-net collections often contain immature males
and females, and occasionally mature males of Calzgus,
especially of Caligus rapax. Amongst these some may be
found with a large notch in the middle of the frontal
margin. This is due to the breaking of the chitinous
filament by which they were secured to their host. The
metamorphosis is a progressive one.

I.—LEPEOPHTHEIRUS (Miller).
This species was first described by O. I’. Miiller* under
the name Lernwa pectoralis.

MoprE or OccURRENCE.

Lepeophtheirus pectoralis is most frequently found upon
the ‘“‘white fluke” or flounder (Pleuronectes flesus). It
also occurs on the plaice, dab, sole, &e. It does not con-
fine itself to any particular part of the exterior. Males and
immature forms of both sexes are to be found all over the
skin on each side of the fish. Mature egg-bearing
females, however, are usually found under the pectoral,
the pelvic, the ventral and the dorsal fins. With careful

* Prodrom. Zoolog. Dan., 1776.

68

examination it is possible to collect a series of these
parasites, from the early “‘chalimus” stage to the adult
condition, from one fish. Sometimes only a few speci-
mens occur on the fish. At other times large numbers
are to be found. It is by no means rare to find between
twenty and thirty mature females under each pectoral
fin alone, as in the case which is illustrated in the cut. One
hundred specimens of another species, L. heppoglossi, have
been collected from the ‘‘ white” side of a halibut in the
Aberdeen Fish Market. The average length of a mature

Lepeophtheirus pectoralis, 32 specimens, on the pectoral fin of a Flounder,

from a photograph.

ege-bearing female is one-fifth of an inch, and of a male
one-ninth of an inch. A mature female measures about
one-tenth of an inch at its greatest breadth, and a male
one-twelfth of an inch. These parasites attach themselves
to the fish by means of their powerful second maxillipedes,
assisted by the antenne, and a decided pull has to be
exerted before they can be torn away. By depressing
the edges of the carapace and applying them closely to
the skin, the parasite can increase its: holding power to
such an extent that the posterior end can be torn from the

anterior part without detaching it. The anterior part,
when thus separated from the posterior, retains its vital
powers for at least twenty-four hours. At first it swims
about vigorously, but after some hours begins to get
sluggish in its movements, and then finally dies. The
posterior part does not live long when separated from the
anterior. The parasites can be kept alive in sea water for

upwards of six weeks after removal from the fish.

EXTERNAL CHARACTERS.

The animal is depressed dorso-ventrally, and is of a
more or less oval shape, and distinctly divided into four
parts (Plate I., fig. 1). The foremost one of these parts,
and usually the largest, is almost circular in outline, and
has all the appendages, with the exception of the fourth
and fifth pairs of feet, attached to it. This part is known
as the cephalo-thorax.

Viewed from above, this region is seen to be slightly
convex and divided into four portions by imperfect
sutures. Two of these sutures are longitudinal, and
separate the lateral parts of the region from the central.
The remaining suture joins the centre of the two longi-
tudinal sutures like the cross line of the letter H, dividing
the centre of the cephalo-thorax into an anterior and a
posterior portion, of which the anterior is the greater.
There is also an apparent suture near the frontal margin.
The frontal margin is indented, the greatest depth being
in the middle line. This indentation to some extent is due
to the sear caused by the breaking away of the filament
for attachment in the “chalimus” stage. In the centre
of the hollow, situated on the ventral surface, is an oval-
shaped opening (6) with a chitinous fringe. This ts
evidently a sucker, and represents the remains of a median

sucker which is considerably developed during the * chali-

70

mus” stage, when the maxillipedes are rudimentary. Pro-
bably in the adult, it acts as a first aid in securing the
animal to its host. Passing backwards from this sucker,
but distinctly over it, there is a transparent rod (c, fig. 1,
Plate I.; fig. 3, Plate III.), lying inside a triangular
blood space, which terminates in a gland (cg, fig. 3, Plate
Ill.). The gland is probably the organ that secretes the
substance for the filament in the ‘‘chalimus”’ stage and
the rod the remains of the filament. The filament and
duct are in actual contact during the early part of the
parasite’s life (Plate I., figs 4 to 6, c). The eyes, two in
number, are situated in the middle of the cephalo-thorax.
The frontal and lateral margins are surrounded by a trans-
parent membrane with faint transverse lines. This
membrane is simply an extension of the chitinous exo-
skeleton which covers the whole animal. It has
frequently a serrated edge caused by tearing.

The second part of the body is very small, and repre-
sents the fourth thoracic segment of the pelagic Copepoda.
The fourth feet are attached to the external margins of
this segment.

The third part of the body known as the “ genital
segment,’ is of variable shape, according to the degree
of maturity of the reproductive organs. In an immature
female (Plate II., fig. 6), it is usually very little larger
than the fourth part, whilst in a mature one it is nearly
as large as the cephalo-thorax. The genital segment of a
mature female is somewhat quadrangular in outline,
shghtly wider posteriorly than in front. The same
segment in a mature male (Plate I., fig. 2) is oval in shape
and about one-third wider than the fourth part.

The fourth part of the body is short and narrow, being
only one-fourth of the width of the female genital seg-
ment, and corresponds to the abdomen of the pelagic Cope-

FQ

poda. There is an incomplete articulation near the
middle. At the apex of the abdomen there are two short
papille known as the furca or caudal stylets, which
usually have four or five plumose hairs on their posterior
margins.

There are twelve pairs of appendages* (Plate IT., fig. 1)
as follows: —One pair of antennules, one pair of antenne,
one pair of mandibles, two pairs of maxille, two pairs of
maxillipedes, and five pairs of feet, the first three pairs of
feet only being adapted for swimming.

The eyes appear as a reddish spot in the living animal,
and are situated on the dorsal surface mid-way between
the frontal margin and the transverse line of the cephalo-
thorax. When this spot is examined microscopically
(Plate III., fig. 13) it is found to consist of two lateral
eyes closely approximated, embedded in a mass of reddish-
black pigment, and wholly under the carapace. Hach eye
has a simple, spherical, crystalline lens, beneath a thin
cornea. Behind the lens is a row of retinal cells of fairly
large size, lined internally with a tapetum or pigment
layer. A chitin division lined with deep red pigment
separates the two eyes. The earlier Zoologists had con-
siderable doubt as to the true position of the eyes, some
even believed the animals were’ blind. Others
mistook the semi-circular suckers on the frontal margin
of Caligus already referred to for the organs of vision,
giving them the name “ Binoculus.”’

The antennules are placed at the external margin, just
behind the suture on the frontal plate, and each consists
of two joints. The basal joint is much larger than the
apical, and is clothed on its upper margin with plumose
sete.

* The minute details of the jointing and sete of the appendages are not

shown in these figures.

12

The other appendages are all on the ventral surface.
The first are the antenne. These consist each of two
joints, a short stout basal one, and an apical one in the
form of a strong prehensile claw. The antenne are used

to assist the second maxillipedes in grasping.*

The apex
of the claw projects into a small cup in front of the first
maxille.

The mandibles are enclosed in the suctorial mouth
(Plate IT., fig. 8). They are stvlet shaped, and composed
of four joints. The apical joint of each mandible is
flattened, curved inwardly, and serrated on its inner
margin. There is no mandibular palp.

The appendages described here as the first maxille are
given that name with some doubt. The pelagic Copepoda
have only one pair of maxille, which correspond to the
second pair in this memoir. The identification of the
appendages now to be described as maxille is based upon
the fact that they are innervated by a nerve from the sub-
esophageal ganglion that has its origin just anterior to
the nerve supplving the maxille proper. The first maxille
consist of one joint which is considerably swollen at the
base, and tapers to a sharp point at the apex, forming as a
whole, a curved claw. Two minute sete are attached to
the basal part, and probably represent the exopodite or
palp. These appendages are situated near the lateral
margins, and slightly posterior to the base of the antenne.

The second maxille are placed at the sides of the
mouth, and consist of a single joint, robust at the base
and dividing into two slightly curved teeth at the apex,
representing the exopodite. There is a distinct endo-
podite, with two sete at its apex, attached to the base of
the anterior surface of the exopodite. The second maxille

* Baird (op. cit. p. 263) describes these organs as the first pair of
footjaws.

73
appear to act as a scraping apparatus for removing the skin
of the host.

The first maxillipedes consist of two-jointed appendages
placed mid-way between the apex of the mouth, when it
is at rest, and the lateral margin. Their chief function
is apparently to keep the mouth free from obstruction.

The second mawxillipedes situated near the middle line,
mid-way between the first maxillipedes and the first pair
of feet, are composed of two joints. The basal joint is
considerably swollen and the apical is in the form of a
powerful claw, which closes upon the basal joint, forming
a strong grasping apparatus. According to Claus, and
others, the first and second mavxillipedes are really only
the exopodite and endopodite of one and the same
appendage.

The first three pairs of feet consist of an endopodite
and an exopodite attached to a two-jointed protopodite.
In the first pair the endopodite is rudimentary, and is
represented by a single minute joint bearing a few sete
at its apex. The exopodite is two-jointed. In the second
pair both the endopodite and exopodite are three-jointed.
The third pair has the protopodite well developed, form-
ing a lamella. The endopodite and exopodite are very
small, the former being composed of two joints and the
latter of three joints. Each of the first three pairs of feet
is attached to a median sternal plate. The exopodite of
the first, and the endopodite and exopodite of the second
and third pairs, are provided with a number of plumose
setee along the internal margins of the joints. The dorsal
and ventral margins of the protopodites of the second and
third pairs of feet are furnished with movable setose
plates. The sterna of the second and third feet are
clothed with sete on the posterior margins. The fourth
pair of feet (Plate I., fig. 1) have two-jointed protopodites,

74

and exopodites also two-jointed, but no trace of endopo-
dites. The external angles of the joints are furnished
with short spines. The fifth pair are rudimentary, are
attached to the posterior end of the genital segment, and
consist of a thin lamella, furnished with three sete along
the posterior margin. Situated on the. middle line
between the second maxillipedes is a strong chitinous
plate with a bifid apex pointing posteriorly. This is
known as the sternal fork, but its function is unknown.*

The external openings are the mouth, the vulve, the
openings of the oviducts and vasa deferentia and the anus.
The mouth (Plate I1., fig. 1 and fig. 8) is situated on the
ventral surface of the cephalo-thorax, and is placed at the
apex of a short, movable, conical tube. This tube is com-
posed of the upper and lower lips fused together. The
vulvee (Plate IT., fig. 6) are situated on each side of the
middle line near the posterior end of the genital segment,

‘

and communicate with the “receptacula seminis.” They
are difficult to see in the adult female, but have each
frequently a spermatophore attached which indicates the
position. The openings of the oviducts are in the same
segment, but nearer the lateral margins and just under
the fifth feet. The openings of the vasa deferentia (Plate
IL., fig. 5) are situated on the postero-lateral margins of
the genital segment of the male. The anus is situated in
the middle line at the apex of the abdomen. In
addition to these more important openings, there are also
apertures of pore-canals and glands on the anterior
surface of the basal joint of the protopodites of the second
and third pairs of feet, and also on the dorsal surface of
cephalo-thorax and abdomen. The opening in some cases

* Mr. I. C. Thompson suggests that the sternal fork appears to him to
be a support or crutch, serving to raise the body sufficiently from the host
to enable either the swimming feet or the mouth organs to be used, but
I have not seen it used in this manner.

75
is at the apex of a small papilla, and communicates with
a sac in the interior.

When resting, Lepeophtherus lies upon the ventral
surface, keeping the first three pairs of feet moving with
spasmodic jerks. When irritated, as in attempts to remove
them from their host, the males and immature females
move very rapidly over the skin of the fish. The mature
females make no attempt to escape, only clinging more
securely. On transferring them to clean sea water they
settle on the sides and bottom of the vessel, and sometimes
adhere to the surface film of the water, remaining quiescent
for long periods. When the water is shaken slightly they
detach themselves and swim about rapidly on their backs.
They soon tire, however, and return to rest again. Lepeo-
phtheirus makes no attempt to leave the water when kept
in small aquaria. The allied form, Caligus, on the other
hand, crawls out of the water and up the sides of the
glass, where it remains, making no attempt to return, and
soon dies owing to the evaporation of the water from
under the carapace. These parasites are very tenacious
of life, and live for a considerable time after the host has
died if they are not allowed to dry up. In some instances,
although the host had been dead over twelve hours, and
the parasites to all appearance were also dead, they
soon revived when placed in sea water. Increase of
temperature to 16° C. and over is fatal to them. They
can, however, stand very considerable decrease of tem-
perature. On one or two occasions during February,
1900, the small aquaria in the tank room at Piel, some
of which contained parasites under observation, were
frozen, and the temperature of the room itself stood at
—1°C., but the parasites suffered no harm. They can also
be kept alive in sea water for weeks without change if the
aquaria are kept cool.

76

The colour of the living animal varies with the position
in which it lives. On the dark side of the fish they are
of a deep brown, almost black, colour. On the “white”
side and under the fins they are nearly colourless, due to
the contraction of the pigment cells, which appear as
brown spots under the microscope. The dark coloured
forms soon become almost colourless when exposed to
light.

Tuer Bopy-watLt AND Bopy-caVITY.

The body-wall consists of (1) the chitinous cuticle or
exoskeleton, which has been described in the external
characters, (2) the cellular hvpodermis, and (3) the con-
nective tissue laminew which line the integument, traverse
the body cavity, and support the alimentary canal and
other organs. The only cavity left inside the body-wall is
the system of lacune, in which the colourless blood flows
(see below under blood system, p. 81).

THE ALIMENTARY CANAL.

The mouth, already described, leads into a short, narrow
curved oesophagus, lined with a thin chitinous coat which
is continuous with the exoskeleton. Near the anterior
end the chitinous coat is much folded. The cesophagus
(Plate ITT., figs. 5 and 5) passes through the anterior part
of the nervous system, and in a transverse section of that
region appears as a minute pinhole. After leaving the
nervous system, it courses over the sub-cesophageal gang-
lion, and under a short cecal projection of the stomach,
finally entering the stomach on its ventral aspect, at the
posterior end of the sub-cesophageal ganglion.

The stomach lies along the ventral surface, and is
lageniform in shape (Plate IT., fig. 3). At the anterior
end it is produced into a short cecum which extends over
the posterior end of the esophagus and it terminates by

- |

|
opening into the intestine in front of the second pair of
feet.

The tmtestine is the direct continuation of the stomach.
It commences in front of the second pair of feet, and
passes through the thoracic and genital segments into the
abdomen. It widens slightly behind its junction with
the stomach, and then contracts as it passes through the
fourth thoracic segment. It expands again in the genital
segment, and contracts as it enters the abdomen. It
terminates in a short rectum leading into the anus at the
apex of the abdomen. ‘There are no convolutions in this
alimentary canal.

The intestine at its anterior end lies on the ventral
surtace of the animal. In the centre where it passes
through the genital segment, it courses along the dorsal
surface. It bends down as it approaches the abdomen,
and occupies the centre of that part of the body. In
transverse sections of a mature female the stomach is
iriangular in shape, with the apex pointing dorsally. The
intestine in the genital segment is also triangular in
transverse section, but the apex is directed ventrally. In
immature females the stomach and intestine are of almost
circular outline when cut transversely, so that the
alimentary canal is considerably compressed when the
reproductive organs arrive at maturity.

The wall of the whole alimentary canal is lined with a
thin layer of chitin continuous with the exterior. In
many places it is considerably broken up, giving it the
appearance of fine striation. Underneath the chitin is a
layer of nucleated cells, which extends from the posterior
portion of the esophagus to the rectum. There does not
appear to be any marked regional differentiation in the
cells. The lining of the stomach and intestine is thrown
into a number of longitudinal folds (Plate III.,fig. 11), the

78

height of which varies considerably. In the anterior por-
tion of the stomach these folds are very little higher than
the general line, but as they pass posteriorly they increase
considerably, diminishing again in the intestine as they
approach the rectum. The greatest height of the folds
is reached in the portion of the intestine passing through
the genital segment. In the intestine and posterior por-
tion of the stomach there are a number of glandular cells,
usually at the apices of the longitudinal folds, the contents
of which stain deeply with eosin. In many of these the
cell contents have disappeared, leaving a clear space,
only the cell wall remaining.

The wall of the stomach and intestine is marked by a
series of transverse constrictions, giving it a crenate
appearance, which is easily seen in the hving animal. In
the hving animal an intermittent movement of the intes-
tine and stomach is kept up. The action is wave-like,
starting at one end, and passing to the other. After con-
tinuing in one direction for a time, it reverses and passes
the opposite way. There is no valve between the stomach
and intestine, and when the peristaltic motion is reversed
the fluid in the intestine is sent back into the stomach
again. The only portions of the alimentary canal that
can be closed are the esophagus and anal end of the
rectum. The former is controlled by two longitudinal
muscles which compress it, the latter by a number of
muscles passing obliquely to the body-wall at the sides of
the abdomen. The fluids contained in the alimentary
canal are usually colourless, but occasionally when taken
direct from the fish and placed under the microscope, a
reddish tint may be detected at the posterior end of the
cesophagus.

In connection with the alimentary canal there is a
distinct paired digestive gland (Plate IL., fig. 3 and fig. 9).

yi)

It consists of three portions, two moderately large
masses on the lateral margins of the cephalo-thorax,
just behind the antennules, and a median, smaller one, in
front of the base of the mouth. The lateral portions are
connected with the median by a duct. The median por-
tion gives off a duct, which passes posteriorly along the
cesophagus and enters the cecum at the anterior end of
the stomach. When the parasite is first removed from the
fish the digestive gland is usually of a dark brown colour,
but after starving for a few weeks it becomes colourless.
The product of the gland is a pale, yellow fluid, which
can be seen as it passes along the duct between the lateral
and median portions.

Situated between the first and second pairs ot thoracic
feet is a pair of glands visible in the lying animal as
brown spots. A minute duct passes downward and then
forward along the stomach. The duct appears to enter
the stomach near the posterior end.

The food of this parasite is said to be mucus, and blood
has not been detected in the stomach.* This fact gives
some cause for the opinion advanced by many Zoologists
that Lepeophtheirus and other allied genera are therefore
not parasites in the strict sense of the term, and may not
be hurtful to their hosts. There is considerable difficulty
in settling the question of their true food. Specimens
taken direct from the living fish and placed under the
microscope, rarely show even the faintest trace of red
colouring matter in the alimentary canal. The difference in
structure between the Caligide and the obviously blood-
sucking Lernez is very great. This will be pointed out
in the section dealing with Lernea branchialis, and may
account for the apparent absence of blood. Mucus at the
best is a poor food, but Lepeophtheirus can live for upwards

* They do not hesitate, however, to eat their comrades when these
become feeble.

of six weeks in filtered sea water without visible food of
any kind.

From the large numbers of flounders examined in the
Piel laboratory, partly in connection with this memoir,
but chiefly in connection with fisheries work, during the
past year or two, the conclusion has been arrived at, that
Lepeophtheirus pectoralis to some extent feeds on blood,
and may be hurtful to the fish, especially when present
in numbers (see figure on p. 68).

The appendages are more suited for a sedentary life
than even a semi-pelagic one. ‘The animals can only
remain swimming for short periods, and their presence in
tow-nettings, therefore, is accidental. They do not, under
normal conditions, and as long as the fish remains in a
healthy state, leave their host. In the fish tanks at Piel
over 150 flounders, all more or less infested with
Lepeophtheirus, are kept during the spawning season.
The waste water from the tanks is carefully filtered for
periods of at least three months in the spring, to collect
the eggs shed by the fish. Yet not even one specimen of
the parasite has been found in the filter. When the
fish are examined and the parasites removed, no matter
how carefully, the skin, especially where there are a
number close together, is usually lacerated and bleeding.
The males and immature females on the general surface
of the body do not seem to remain long enough in one
place to cause obvious injuries. Under the fins, however,
and on the fins themselves, where the egg-bearing females
are usually found, and where they le for weeks in the
same position if not disturbed, is the part of the fish
chiefly injured. The pectoral fin in some instances may
be partially destroyed, and pieces of the tissues are fre-
quently found enclosed in the second maxillipedes of the
parasite.

$1

The antennz and claws of the second maxillipedes are
plunged into the tissues of the fish along with the teeth
of the maxilla, lacerating the skin, and into this wound
the suctorial mouth is directed. The blade-like mandibles
assist in collecting the particles of food material. These
ave sucked up, pass down the oesophagus into the stomach,
where they are at once acted on by the fluid from the
digestive glands, and the colour of any blood present may
then be discharged. It is usually at the junction of the
esophagus with the stomach that any red coloured
particles occur. The food can then be traced along the
stomach and intestine, and the waste matter is expelled
from the anus in long strings.

On comparing transverse sections of the alimentary
canal of Lepeophtheirus and of Lernea which happen to
contain food, and have been stained in eosin and hema-
toxylin, there is seen to be a marked similarity in the
nature of the food in the two cases. Both are finely
granular, and stain red with eosin. Mucus from the
flounder has no such granular appearance.

It is stated by some Zoologists that copepod parasites
are generally found most abundantly on weak and
diseased fishes. It is not so with Lepeophtheirus
pectoralis. Flounders with many parasites in our tanks
were in as good condition as those that had none. They
were never found on flounders which were thin and in
poor condition, as they detach themselves and swim away
when the fish becomes feeble. This was proved by actual

experiments and observations at the Piel Hatchery.

THE Bioop anp CIRCULATION.

There is no heart in Lepeophtheirus, nor are there any
proper blood vessels.
F

82

The circulation is wholly lacunar, and simply consists
of broad, irregular streams passing through the spaces
left among the internal organs, and between the connec-
tive-tissue bands of the body-wall. These streams have in
general certain definite directions, but they are not
uniform, continuous currents. The fluid advances by
successive jerks, depending upon the movements of the
alimentary canal and, in part, of the reproductive system.
The blood is a clear fluid, containing numerous colourless
corpuscles. The corpuscles vary in size and shape, and
can accommodate themselves in diameter to the spaces
through which they pass.

Plate IT., fig. 2, shows the course of the main blood
currents. Starting from behind the eye, there are two
currents passing posteriorly, one flowing to each postero-
lateral angle of the cephalo-thorax, where it turns and
courses forward along the lateral margin of the carapace
till it reaches the group of muscles connected with the
mandibles. It then divides, one portion continuing along
the margin to the base of the antennules, where it splits
up into minute currents, all converging to the base of the
mouth, while the other branch of this cephalo-thoracic
current passes along the muscles of the mandibles and
duct of the digestive gland, and meets the currents of the
former branch at the base of the mouth.

A second main current courses posteriorly through the
cephalo-thorax and the fourth thoracic segment, into the
genital segment. It flows there along the reproductive
organs in a broad stream, and turns round at the end of
the segment. The currents from both sides meet in the
middle line, and flow forward under the alimentary canal.
In the region of the second maxillipede, this median
ventral current breaks up into a complicated series of
smaller currents, some of which pass into the two currents

)
83

flowing posteriorly, and the others into the currents
passing to the base of the mouth.

The main currents are easily seen by placing the living
animal on its back, in a drop of sea water on a slide. then
covering with a thin cover glass and examining with a
tin. objective.

The blood currents described above do not continue to
flow for any length of time in the one direction. At one
period they may be flowing as indicated by the arrows in
Plate II., fig. 2. Then they suddenly slacken and reverse,
and stream for a time in exactly the opposite course.
Sometimes the blood corpuscles are seen to simply oscillate
backwards and forwards, making no advance, but at other
times they pass rapidly along in a definite manner.

There are no independent organs of respiration. It has
been suggested by Hartog and others that the blood is
probably aerated from the sea water contained in the thin-
walled alimentary canal by the method of “anal respira-
tion,” which has been described in Cyclops, Caliqus,
Argulus, Daphnia, Cypris and other lower Crustacea.

The cuticular exoskeleton over the surface of the body
is in most places so thick that the respiratory change of
gases may be supposed to take place much more readily
through the very thin layer of chitin which lines the
rectum. There are dilator muscles attached to the wall
close to the anus, and the peristaltic movements of the
whole alimentary canal may aid in the production of
inhalent and exhalent currents of water. It appears,
however, to the present author that further precise obser-
vations are required to substantiate this hypothesis.

No organ corresponding to the “shell gland” described
in. various lower crustacea, and shown by Claus, Hartog

and others to be a renal organ, has been found.

S4

THe Muscutar System.
The muscles moving the appendages and segments of

the body can be distinctly seen and traced to their
extremities through the transparent exoskeleton (Plate IT.,
fig. 1 and fig. 2).

The frontal portion of the cephalo-thorax is controlled
by two short slender muscles, m//., (Plate II., fig. 2) passing
postero-laterally from near the lateral edge of the cara-
pace. They act in depressing the margin so as to produce
a close attachment to the host. The posterior region of
the cephalo-thorax is supplied with a number of pairs of
muscles, some passing forward and others laterally, which
contract and expand that part of the body. The lateral
margins are controlled by long muscles passing obliquely
outwards from the anterior end of the lateral suture.
The muscles of the fourth thoracic and genital segments
arise near the median line of the posterior portion of the
cephalo-thorax, and pass backwards. They produce a
lateral motion of the posterior parts of the body, and also
a sort of telescoping contraction which draws the genital
segment into the cephalo-thorax. The muscles of the
abdomen arise near the middle of the genital segment
and pass backwards. They produce a telescoping move-
ment of the abdomen.

The various appendages and other organs are also well
supphed with muscles. The antennules have each a pair,
which elevate and depress the joints. The grasping
action of the antennz is produced by muscles passing
obliquely to the lateral margins. The movements of the
mouth are controlled by a complicated series of muscles
passing anteriorly, posteriorly and laterally, all of which
assist in elevating and depressing it when sucking up

food. ‘The mandibles are provided with muscles of extra-

~

ordinary length and power, which pass obliquely back-
ward to the lateral margins of the carapace nearly opposite
the first pair of feet. The muscles of the first maxille
are very short and thin. They pass along the posterior
surface of the muscles of the antenna, to the lateral
margins. The second maxille are controlled by powerful
muscles passing to the lateral margins. The muscles of
the first maxillipedes pass obliquely forward to the lateral
margins. The second maxillipedes are supplied with short
and powerful muscles which pass forward under the
second maxilla. The terminal claw is, provided with
muscles of great strength. The first three pairs of feet
are supplied with a complicated series of muscles passing
dorsally amongst those controlling the posterior portion
of the cephalo-thorax. The fourth pair of feet are
apparently little used, and consequently are only supplied
with feeble muscles. The alimentary canal is controlled
by longitudinal muscles, and also by muscles passing
transversely, which produce the wave-like peristallic
motions and crenated appearance. The anus is opened
and shut by muscles passing obliquely, which open and
shut each side alternately or simultaneously according to
the requirements of the animal. The reproductive organs
are also controlled by muscles, which give rise to pulsating
movements, and assist in expelling the ova and
spermatophores.

Tue NerRvous SYSTEM.

The central nervous system in Lepeophthevrus consists
of a cerebral or supra-cesophageal ganglion and a large
sub-cesophageal ganglion placed on the ventral surface,
in the median line, and extending from slightly in front
of the second pair of maxille to near the articulation of
the second pair of maxillipedes with the body. The

56

ganglia are connected by broad commissures passing on
each side of the esophagus, leaving only a narrow opening
for its passage. The sub-cesophageal ganglion projects
slightly forward under the supra-csophageal, giving it
the appearance of being separated from it, when viewed
from the ventral aspect (Plate III., fig. 2). These are
the only ganglia, and they supply the various parts of the
body with nerves.

The supra-csophageal ganglion is about half the size
of the sub-cesophageal. It is produced on its dorsal
surface into an optic lobe (Plate III., fig. 5), from which
arises a distinct pair of optic nerves. Horizontal sections
of the optic lobe show that the roots of these nerves cross
each other (Plate III., fig. 12). Hach optic nerve, there-
fore, is supplied by fibres from both sides of the brain.

The nerves supplying the antennules arise from near
the anterior angles of the ganglion. They pass obliquely
forward to the base of the antennules, and there sub-
divide into a number of branches which pass to the sete
clothing the anterior surface of the basal joint and apex
oi the second (Plate IIL, fig. 4). From the manner in
which the antennules are supplied by this nerve it 1s
evident that they are important sensory organs (Plate IIL.,
fig 4).

The antenne are supplied by nerves arising from the
anterior angles of the ganglion, which pass anteriorly
under the nerves of the antennules and enter the base
of the antenne. These are the only appendages suppled
from the supra-cesophageal ganglion.

The sub-cesophageal ganglion is heart-shaped, and fully
twice the size of the supra-cesophageal. It represents the
whole of the thoracic and abdominal ganglia of the higher
crustacea, and supplies the remainder of the appendages.

S7

The nerves passing to the mandibles have their origin
on the anterior margin near the middle line. They
course along the muscles of the ceesophagus, and reach the
mandibles near the base of the mouth.

The next pair of nerves arise at the anterior angle of
the ganglion, course forward, under the nerves of the
antenne and antennules, to the frontal plate which they
enter about midway between the lateral margin and
middle line. They then turn abruptly and pass out to
the lateral margins of the frontal plate, just above the
antennules. The margin at this point is destitute of the
transparent membrane which surrounds the carapace.
The nerves terminate in a shallow cup, evidently a
sensory organ.

Three other pairs of nerves arise from the anterior
angles of this ventral ganglion. The first passes to the
rudimentary first pair of maxille, the second, a short
nerve, passes to the second pair of maxille, and the third
to the muscles controlling the lateral margins of the
cephalo-thorax.

The nerves supplying the first pair of maxillipedes arise
from the anterior portion of the lateral margin. They
are large nerves at their origin, but immediately divide
into four branches, passing to the maxillipedes and
muscles. The second pair of maxillipedes are also supplied
by nerves arising from the lateral margins. Like those
of the first maxillipedes they have strong roots, and at
once divide into three branches which pass to the second
maxillipedes and their muscles.

The remaining nerves have their roots in the posterior
end of the ganglion. There are three pairs. These
supply the five pairs of feet and the abdomen. The outer
pair of nerves supply the first pair of feet. Near the
origin a branch is given off which passes to the muscles

85

of the stomach. The next pair supply the second pair of
feet. They course along the median nerves as far as the
sternal fork and then diverge. Just under the sternal
fork a branch is given off which appears to pass to the
muscles of the posterior region of the cephalo-thorax.

The median pair course close together, and unless
carefully examined are easily mistaken for a single nerve.
There is a distinct division, however, which is apparent
even in the roots. Between the second and third pairs
of feet a strong branch is given off which passes to the
third pair of feet. The nerves then diverge, and just
before entering the fourth thoracic segment give off a
branch that passes to the fourth feet. The main trunks
course on through the genital segment, still further
diverging. Shortly after entering the broad part of this
segment a third branch is given off which takes a semi-
oval course along the ventral surface of each half of the
segment, finally passing to the sete of the fifth feet. On
entering the abdomen the main trunks split into two
branches, one passing to the anus and the other to the
sete on the apex of the caudal stylets (Plate III., fig. 2).

Each nerve, after leaving the main trunk, sends out
numerous branches which pass to the various muscles
controlling the appendages innervated by that nerve.
[xcepting the nerve passing to the fifth feet, the branches
are not shown in the figure (Plate III., fig. 1). There
is considerable difficulty in tracing the endings of the
branches when they pass amongst the muscles.

The chief sense organs connected with the nervous
system are the conspicuous eyes which are described above
(p. 71). There are also the numerous sete scattered over
the surface of the body and appendages, which are possibly
tactile in function. Probably the setae upon the anten-
nules, which are richly supphed with nerves from the

t *

89

supra-cesophageal ganglion, have a special function, which
may be olfactory.
THe RepropucrivE OrGaANs.

The reproductive organs are paired, and as already
stated, the sexes are separate.

In the female (Plate II., fig. 4) the ovaries are large
kidney-shaped organs lying on each side of the anterior
portion of the stomach and extending from under the first
pair of feet to the base of the second maxille, when
fully matured. Each oviduct (od.) arises near the anterior
end of the ventral surface of the ovary, and courses
posteriorly as a narrow tube till it enters the genital
segment. It then expands rapidly, and passes to near the
end of the segment. It then reverses its course, passing
forward to the central portion of the segment, where it
turns again in a posterior direction, and passing out to the
centre of each half of the segment, it opens to the exterior
just under the fifth feet. Hach oviduct thus forms two
loops in the genital segment. On the ventral aspect of
the loops of each oviduct there is a short, semi-transparent
eylindrical tube (sg.) with the anterior end closed and
rounded, and the posterior produced into a fine duct,
which communicates with the oviduct near its extremity.
This organ is evidently a cement gland for secreting the
enclosing membrane of the ovisac. Each yulva (fig. 6, vw.)
is situated near the middle line behind the junction of the
genital segment with the abdomen. It appears to consist
of a simple opening leading into the vagina which expands

‘

into a “‘receptaculum seminis.” This is an elongated sac
passing from the median line to the oviduct, which it
enters alongside the duct of the cement gland.

In the male the reproductive organs (Plate II., fig. 5)
consist of a pyriform testis, on each side, situated in a

position corresponding with that of the ovary. It is only

90

about one-fourth the size of the ovary. Hach vas deferens
courses posteriorly into the oval genital segment. It com-
municates with the sac of the spermatophore on the external
margin near the posterior end. <A short cement gland
furnishes a duct which passes in at the anterior end of
the sac. The spermatophore, an oval body containing
the spermatozoa, is expelled from an opening near the
posterior angle of the segment.

In Lepeophtheirus the fertilisation of the female is
accomplished soon after the “chalimus” stage 1s com-
pleted. The genital segment is then very small, about
one-fifth the length of that of a mature female. It is
grasped by the male on the dorsal aspect. The antennz
close round the junction of the genital segment with the
fourth thoracic, and the second mavillipedes seize the
segment immediately in front of its junction with the
abdomen. ‘The animals remain in this condition for some
time, and can only be separated with difficulty. The
spermatophores are discharged in pairs. When they are
ready for discharging the male folds the whole of the
posterior portion of its body along the ventral surface of
the female. The openings of the spermatophore sacs are
thus brought in contact with the vulve. The spermato-
phores are then discharged, and being in a viscid condi-
tion, at once stick to the female. One end of the cover-
ing, probably the last part that leaves the opening, is
drawn out into a fine thread, which helps to secure the
spermatophore. The spermatophores are not, apparently,

always fortunate in reaching the vulve. It is by no
means uncommon to find them planted amongst the
appendages in little clusters ike grapes. These have

been mistaken by some of the earlier Zoologists for the
eggs, when the true egg sacs were considered to be
antennules.

91

One copulation apparently fertilises all the eggs pro-
duced by the female. It is obvious, when one compares
the male with a mature female (Plate L., figs. 1 and 2),
that fertilisation cannot be accomplished when the female
genital segment is fully developed. Hence the need of
it being effected at an early stage.

The exact period at which the eggs are fertilised by the
spermatozoa is unknown. The spermatophores may be
found attached to the body for some time after the female
has begun to produce eggs (Plate IT., fig. 4, sp.), but they
are then simply empty sacs. Plate Il., fig. 7, shows a
pair of spermatophores that have been detached from an
egg-bearing female. The little opening at d. was in
direct communication with the vulva. These sacs were
empty. In an immature female (Plate II., fig. 6), the
vulva leads into a short vagina, passing directly into the
oviduct. The spermatozoa probably remain in the vagina

‘

which becomes a “ receptaculum seminis.” In: transverse
or longitudinal sections through the region of the vagina
of a mature female masses of spermatozoa are frequently
found in the swollen part (Plate I1., fig. 4, rep.). The
oviduct in the immature female has no communication
with the exterior except through the vulva.

The ovary of a mature female appears as shown in
Plate IIL., fig. 10. It consists of a number of tubules
lined with nucleated cells representing a germinal epithe-
hum, which will form the eggs. The interior of the
tubules is filled with a granular substance, staining faintly
blue with hematoxylin and eosin. When the eggs become
mature the walls of the tubule break down and the eggs
pass out into the oviduct. They are then very small, about
‘)2 mm. in diameter, and do not fill up the duct. Thev
are simply nucleated cells. As they pass posteriorly they

increase in size. In the fourth thoracic segment they

92

measure ‘06 mm., and appear as oval bodies with a thin
vitelline membrane. The cell contents are finely
granular. The nucleus is a large oval body, with a sharp
outline. A single rounded nucleolus is also present.
After passing into the genital segment the cell contents
increase in amount, causing a great enlargement of the
egg, which finally passes out at the opening between the
vulva and the lateral margin of the segment, already
described. As the eggs pass out they are probably
fertilised by the spermatozoa from the “ receptaculum
seminis.” They are then enclosed in a thin chitinous
tube, secreted by the cement gland, which gradually
extends as more eggs are expelled. The ovisacs are often
longer than the animal. The eggs in this tube are
biscuit-shaped, measuring “36 mm. in diameter and
‘11 mm. in thickness. They are arranged in a single
column. When the animal is irritated the tubes are
frequently detached. When the embryos hatch, the
empty, ruptured tube is left, and remains attached to the
animal for a time. After examining many specimens,
the conclusion has been come to that additional eggs are
not developed in the tubules of the ovary after the first
lot have been expelled. Adult females in which the
ovary is only an empty sac are not uncommon.

Lire Hisrory.

Lepeophthewus has no regular breeding season. Mature
females with ovisacs may be found at all times. The
state of development reached by the embryos carried by
various females collected at the same time is frequently
widely different. In some the germinal dise has just
begun to segment, in others the larve are ready to hatch.

The changes that take place in the developing embryo
have not been worked out by the author. The period of

93

incubation was found to extend over several weeks at
least. In one case the ovisaes were kept for six weeks,
and in another eight weeks, before the embryos hatched.
The incubation takes longer than that, however. In
both cases the embryos were pigmented when placed
under observation. The first appendages that make their
appearance are the antennules, antenne and mandibles.
They are in a rudimentary state, and the embryo is now
ready to hateh. During this period the embryo increases
in size as it develops.

The whole of the embryos contained in the tube hatch
practically at once. The enclosing membrane ruptures,
then the membrane of the tube splits, and the nauplii
after freeing themselves from the fragments swim to the
surface. Plate I., fig. 5, represents a newly hatched
nauplius, the natural size of which is "46 mm. It leads
a pelagic life for a time, and grows by successive moult-
ings. It next settles down on some fish, and passes into
a evelopoid state (Plate I., fig. 5). The young parasite
immediately develops a thin chitinous filament from the
median frontal gland already described, which passes into
the tissues of the host, and it becomes fixed. The median
sucker (b., Plate I., fig. 5), with the help of the rudi-
mentary antenne and second mavxillipedes, enables the
animal to bring its mouth into contact with the host.

If young plaice, flounder, cod, &e., one to three inches
in length, be examined very carefully at the end of the
summer, it is practically certain that some recently
attached Lepeophtheirus or Caligus will be found either
on the fins or some other part of the integument. On
examining fins which have parasites attached, the filament
is seen passing through the skin, under it, and along one
of the fin ravs, as shown on Plate I., fig. 5 (natural size
mm.). The filament may have the end bluntly

yy
Lye

94

pointed or flattened into a dise (Plate I., fig. 4). This is
the ‘‘chalimus”’ stage referred to on previous pages, so
called because Burmeister, in 1831,* described it as a new

oe

genus under the name ‘ Chalimus.” This was afterwards
shown by Hesse and others to be only a young stage of the
Caligide. The young parasite continues to grow by suc-
cessive moultings, and the various appendages make their
appearance in regular order. The duration of this
attached stage has not been determined. When the
appendages are fully developed, as in Plate I., fig. 6, the
filament separates at its junction with the frontal margin
leaving a notch, the remains of which persist all through
the adult life.

The male, at the conclusion of the attached stage, is
practically fully developed. The female remains in an
immature condition until fertilisation is effected and the
ova begin to pass down the oviducts. The genital seg-
ment then increases in size from that shown on Plate IT.,
fig. 6, to the mature condition of Plate I., fig. 1.

* Nov. Act. Acad. Natur. Cur. Bonn., vol. xvii., p. 294.

7

II.—LERN AGA.

The Lernx1p.%, although not so extensive a family in
numbers of genera and species as the CaLiGipa, are more
interesting to the specialist. They present some of the
most remarkable instances of retrograde development that
are to be found in the whole group of parasitic Copepoda.
There is great excuse for the difficulty experienced by the
earher Zoologists in giving certain members of this family
their true place in the animal kingdom. ‘The fact that
these animals were placed first in one group and then in
another by successive workers is not surprising, consider-
ing that nothing was then known about their life history.
It requires some study even at the present day to show
that Lernea is a Crustacean, still more to demonstrate
that it is related to Lepeo phtheirus.

The genus Lernea as it now stands contains only five
species. Formerly it was very extensive, and included
many forms, such as Lepeophthetrus pectoralis, that had
not the least apparent resemblance to each other in the
adult state. Careful research, along with a better know-
ledge of the minute structure, gradually eliminated the
unlike species, which were removed to other genera. An
excellent historical account of our knowledge of the group
will be found in Baird’s “ Entomostraca.”

The species described here is Lernea branchialis, Linn.

Mopr oF OccURRENCE.

The adult female is found on the gills of the Gadide,
such as cod, haddock and whiting. Immature (cyclops
stage) males, and females with adult males attached, are
found on the apex of the gill filaments of the flounder,
sometimes in large numbers. Full-grown females are
not plentiful on the fishes caught in the vicinity of Piel.

96

Two to four specimens have been found after examining
numerous catches of young cod of one dozen each. The
ratio thus varies from one in three fish to one in six. In
one or two instances two and sometimes three specimens
were found on young cod eight inches long. The length
of a full grown female Lernwa is a little over one inch.

The adult female is securely fastened to its host by
strong branched horns, three in number, which are buried
in the tissues of various parts of the gill arches. In
many instances the head was found to have actually
penetrated the ventral aorta. To obtain the specimens
in an entire condition the tissues of the host have to be
carefully dissected. Attempts to remove them by force
always result in the head being left in the fish. The
parasite, when once fixed, remains in the same position
throughout life. When it dies the softer parts decay, but
the head continues for a long time embedded in the tissues
of the host, and is often met with there when dissecting
out lving specimens.

EXTERNAL CHARACTERS.

The adult female (Plate IV., fig. 1) is cylindrical. It
is unsegmented, but roughly divided into three parts—a
globular head with anchor-like processes, connected by a
narrow neck to a much swollen posterior part.

The globular head corresponds to part of the cephalo-
thorax in Lepeophtheirus. It is furnished with three
more or less branched horns, two lateral and one median
and dorsal. The head is shghtly curved downwards, ter-
minating in a conical apex.

The anterior portion of the neck represents the
remainder of the cephalo-thorax and the fourth thoracic
segment. The whole of the neck is marked by fine trans-

verse lines.

Ss /

The remainder of the neck and the greater part of the
swollen mass behind corresponds to the genital segment.
The abdomen is represented by the terminal portion of
the swollen part, and gradually tapers to a blunt end.
The swollen region of the genital segment is abruptly
bent into the form of the letter S (Plate IV., fig. 1).

The appendages are rudimentary, the greater number
being entirely absent. Those present are the first pair
of maxillipedes placed at the apex of the head, immediately
under the mouth, and four pairs of swimming feet at the
anterior end of the narrow neck. ‘The swimming feet are
exactly as they exist in the cyclops stage both in size and
structure. The protopodite is two-jointed, the exopodite
of the four pairs is two-jointed. The endopodite of the
first two pairs is also two-jointed. The third and fourth
pairs of feet have no endopodite.

The external openings are, the mouth placed at the
apex of the head, the openings of the oviducts situated
on the ventral aspect of the S-shaped region, and the anus
at the blunt apex of the abdomen (Plate IV., fig. 1, an.).

The colour of the living animal is dark red, due to the
contained blood. When removed from the fish and placed

in sea water the colour changes to white. Lernea does
not live long after being taken from the fish. The
longest period observed was about twelve hours. They

are simply inert sacs quite incapable of movement.
Occasionally the parasites are covered with colonies of
hvdroids which sometimes entirely obscure them. The
exoskeleton consists of a chitinous cuticle moderately thin
and soft in the region of the swollen part, but thick and
hard on the neck and head.

Immature Lernwa branchialis living on the apex of the
gill filaments of the flounder (Plate IV., figs. 3, 4, and 5)
are cyclopoid in appearance. The animal is oval in trans-

G

98

verse section. It is composed of five distinct parts—an
oval cephalo-thorax, three thoracic, and one terminal
segment, representing the genital segment and abdomen.
The anterior portion of the genital segment in the female
is indistinctly divided into eleven joints.

The cephalo-thorax attains its greatest width just
behind the eyes; beyond that point the sides converge
until they reach the first thoracic segment. The cephalo-
thorax is produced anteriorly into a broad blunt rostrum.
In the very early cyclops stage (Plate IV., fig. 3), the
rostrum is further produced into a short triangular
filament which secures the parasite to its host.
The eyes (Plate V., fig. 3) are situated on the dorsal
surface a short distance behind the rostrum. In the
living animal they appear as a dark red spot with a
crystalline lens projecting slightly at each side. When
examined microscopically the structure is found to be the
same as that described in Lepeophtheirus. A thin cornea
encloses a spherical crystalline lens. Behind the lens a
row of fairly large retinal cells is lined internally with a
tapetum layer. A chitinous septum lined with deep red
pigment separates the two eyes. The appendages attached
to the cephalo-thorax are as follows : —

The antennules are placed at the posterior angles of the
lateral margins of the rostrum. They are short, and are
composed of four nearly equal joints furnished with fine
sete.

The antenne are composed of two joints. The apical
joint is provided with a strong claw on its external angle.
The antenne usually project beyond the rostrum, and it
is by means of these that the attachment to the host is
maintained when the filament is broken off.

The mandibles are not enclosed in the suctorial mouth.
They are situated at the base of the lateral surfaces of the

v9

conical tube of the mouth, and consist of two parts. The
basal joint is cylindrical. The second joint is flattened,
and terminates in a broad blade, which is serrated on the
inner margin.

The single pair of maxille are placed at the base of the
mandibles. They consist of two lobes, one of which is
very small. The larger lobe has two moderately long
setee at its apex, the smaller one has one seta.

The first pair of maxillipedes are placed immediately
behind the mouth. They consist of four joints, the last
joint being furnished with a strong claw. The basal
joint has two short hooks near its apex.

The second pair of maxillipedes in the female are rudi-
mentary, and are represented by a minute knob. In the
male they are composed of two joints, the apical one being
in the form of a powerful claw. It is by the aid of the
second maxillipedes that the male grasps the female
during copulation.

The first pair of swimming feet consist of a two-jointed
protopodite, an endopodite and an exopodite, both two-
jointed. The apical joints of the endopodite and the
exopodite are furnished with long plumose sete on their
inner margin and apex. This pair of feet is attached to
the posterior end of the cephalo-thorax.

The second pair of swimming feet is attached to the
first free thoracic segment, the third pair to the second
free thoracic, and the fourth pair to the third. These
free segments really represent the second, third and
fourth thoracic segments, the first being a part of the
cephalo-thorax. The second pair of swimming feet in
every respect resemble the first pair. The protopodites
of the third and fourth pairs are two-jointed; the endo-
podites in both pairs are absent. The exopodites are
similar to those of the first and second pairs. The fifth

100

pair of feet is represented by minute papille. The caudal
stylets are very short, and furnished with three or four
short plumose sete at the apex.

The external openings are the mouth, the vulye, the
openings of the vasa deferentia and the anus.

The mouth is situated on the ventral surface of the
cephalo-thorax, at the apex of a conical tube, composed
of the upper and lower lips fused together. In the very
early cyclops stage the lips are not fused. The vulve and
openings of the vasa deferentia are placed at the posterior
angles of the genital segment. The anus is at the apex of
the abdomen, in the middle line. The vulve open into
the receptacula seminis, which are in direct communi-
cation with the oviduets.

The whole of the genital segment and abdomen in the
female is marked by fine transverse lines. The colour,
which is arranged in patches, varies from dark violet to
hight red.

ALIMENTARY CANAL.

In the adult the mouth opens into the intestine, which
probably acts as the stomach, the cesophagus and true
stomach having disappeared in the metamorphosis of the
cephalo-thorax. The intestine is at first narrow where
it passes through the neck, then it widens considerably in
the swollen part of the genital segment, contracting
shghtly in the abdomen, and finally terminates in a short,
narrow rectum leading to the anus (Plate V., Fig. 4).
The intestine is lined with a single layer of nucleated
cells. Attached to this layer, and in some cases embedded
in it at irregular intervals, are large cells filled with fine
granular material. In some parts these large cells are
grouped together two and three rows high. In other
parts they are quite free (Plate V., figs. 5 and 6). The
layer supporting the nucleated cells appears to be com-

LOL

posed of fine muscle fibres. There is no chitinous inner
lining as in Lepeophtheirus. Between the basement layer
of the intestinal wall and the integument there is a net-
work of muscles passing in various directions. This
tissue represents the body-cavity and body-wall. The
spaces between the muscles are filled with the red blood.
The peristaltic movement of the intestine is similar to that
observed in Lepeophtheirus.

In the cyclops stage the mouth leads into a short,
narrow cesophagus (@, Plate V., fig. 2), which passes into
the comparatively wide stomach on its ventral aspect. The
stomach is lageniform, with the narrow end pointing
posteriorly. On the dorsal aspect, at the anterior end, it
is produced into a short, blunt cecum. ‘The narrow end’
of the stomach connects with the intestine, a long

straight narrow tube, greatly compressed over the region

of the receptaculum semiinis. The intestine terminates
in a very short rectum leading to the anus. The cells

both free and attached along the wall of the stomach and
intestine are similar to those in the adult. Sometimes
the stomach is filled with free cells, which are kept con-
stantly travelling backward and forward by the move-
ment of the intestine. At other times few free cells can
be seen. No trace of blood between the alimentary canal
and the integument, as found in the adult, has been
observed in the young.

- No trace of a digestive gland could be found in the
adult. In the young it is probably represented by a
series of groups of cells running along the lateral margins
of the cephalo-thorax (Plate V., figs. 1 and 3, l.v.). A short
duct could be traced leading from these groups into the
stomach, just posterior to its junction with the csophagus.

When the alimentary canal of a living parasite is
opened, and the free cells are isolated and examined with

102

a high power, they are found to be subspherical, granular,
and of various shades of greenish yellow colour. Some
of the cells exhibit faint amceboid movement. It 1s pro-
bable, therefore, that the digestion is intracellular.

The food of these parasites is undoubtedly blood which
we find in the alimentary canal, but whether the absence
of digestive glands in the adult accounts for its unchanged
appearance has not been ascertained. In the young,
where there is an apparent digestive gland, the contents
of the alimentary canal are not red.

CIRCULATION AND RESPIRATION.

There is no heart or vascular system, and in the adult
no movement of fluids could be observed which would
indicate a blood circulation. The animal is probably
dependent upon the blood sucked from its host for the
supply of oxygen necessary to maintain hfe. It is there-
fore possible that the early death after removal from the
fish is due largely to the inability to take up oxygen from
the water. The blood circulation could not be satisfac-
torily traced in the cyclops stage.

THE MuscuLar SYSTEM.

The muscular system in the cyclops stage, although not
so highly developed, is practically similar to that of
Lepeophtheirus. In the adult female it is simply a net-
work between the integument and the alimentary canal
forming a supporting medium for the latter.

THE NERVOUS SYSTEM.

In the cyclops stage the central nervous system is the
same as in the adult Lepeophthetrus. The nerves supply-
ing the various appendages have also the same origin and
direction as described in that type. The nerves marked
4a, 4b, and 5a in Plate IIL., fig. 2, could not be traced.

a a

108

The nerve supplying the antennules has a similar branch-
ing at its termination to that of Lepeophtheirus.

In the adult Lernea no trace of a nervous system could
be made out, and certainly if present at all it is very much
reduced.

THe REPRODUCTIVE ORGANS.

The reproductive organs of Lernawa, like those of
Lepeophthewus, are bilaterally symmetrical. In the
cyclops stage of the female (Plate V., fig. 1) the ovaries
(o.) are pyriform organs lying on each side of the
stomach. They are situated on the ventral surface near
the posterior end of the cephalo-thorax. Mach oviduct
(od.) arises near the posterior end, and courses posteriorly
as a narrow tube. When it enters the genital segment it
expands rapidly, ending in a large sac, the receptaculum
seminis (s), communicating with the vulva (vu.). The
oviduct has no distinet loops, and no cement gland is
found.

In the adult male (Plate LV., fig. 5) the testes (¢.) occupy
the same positions as the ovaries in the female. The vasa
deferentia are straight, narrow tubes coursing posteriorly
and terminating in the sacs of the spermatophores. A
cement gland is present, as in Lepeophtheirus.

The ovary in the course of the metamorphosis under-
goes great change of position. It is removed from the
cephalo-thorax into the genital segment. It occupies a
harrow region at the apex of the deep indentation (Plate
V., figs. 4 and 5, 0.). The two ovaries have also practically
fused together, no separation is visible in transverse sec-
tion. The united ovaries are produced into horn-like pro-
jections anteriorly and posteriorly (Plate V., fig. 5). The
oviducts (od.) arise near the apex of the anterior horns,

pass across the segment to its ventral surface, and then

104

course along each side of the median line to the external
openings. Hach cement gland (Plate V., figs. 4, 5 and 7,
sg.) 1s a long crystalline organ of nearly the same length
and breadth as the oviduct, lying ventrally to it. The
anterior part terminates at the base of the neck, in a blunt
end. ‘The posterior end communicates with the oviduet
just inside the opening to the exterior.

The structure of the ovary of Lernawa differs con-
siderably from that of Lepeophtheirus. In the eyelops
stage it consists of a mass of minute nucleated cells. In
the adult condition there are no tubules, and all the eggs
are in close contact. The size of the eggs in the ovary
of the adult varies from ‘04 to ‘08 mm. They are of the
same structure and undergo the same changes in their
passage along the oviduct as the eggs of Lepeophtherrus
when they enter the thoracic ends of the oviducts. ‘The
ovisaes consist of long slender tubes very much twisted.
(Plate IV., fig. 1, os.). When straightened out each tube is
often found to attain the length of seven or eight inches.
The eggs are arranged in a single column, and the period
of incubation is of the same duration as in Lepeophtheirus.
The death of the parent or detachment of the ovisacs has
nu effect on the vitality of the embryos.

Fertilisation of the female is effected during the fixed
period of the cyclops stage. The spermatophores are
attached to the female in a similar manner to that
described for Lepeophtheirus. The contents pass into the
receptacula seminis, and the empty sacs fall away. They
are then replaced by others in succession, until the recep-
tacula are filled. Each fully charged receptaculum repre-
sents the contents of four spermatophores (rep., Plate
IV., fig. 4). At first there is a distinct division between
each lot, but this soon disappears, and the whole becomes

one mass of spermatozoa. From a large number of

105

females sectioned in various directions, the conclusion has
been arrived at that the spermatozoa at once pass up the
rudimentary oviduct to the ovary and fertilise the eggs.
This probably accounts for the difference between the
ovary of an adult Lernwa and Lepeophtherrus. No trace

of a receptaculum seminis could be made out in the adult.

Lire History.

The development of the embryo has not been worked
out by the present author. An excellent work by D.
Pedaschenko* contains a full description and figures of
the developing embryo.

The young Lernea hatches out as a nauphus, with
three pairs of appendages, representing the rudimentary
antennules, antenne, and mandibles (Plate IV., fig. 2,
nat. size, “45 mm.). It then after a short pelagic life,
settles on the apex of the gill filaments of the flounder,
to which it adheres by a broad chitinous filament, and
passes into a cyclopoid form (Plate IV., fig. 4). The
young Lernea are occasionally found on the gills of the
plaice and lumpsucker. The parasite, by its attachment
to the gill filament, produces a marked change in that
organ. The whole of the apex assumes a tumid character,
and the filamentous plates on both sides for some little
distance disappear (Plate IV., figs. 8 and 9). While
attached to the gills the various appendages develop. The
male here reaches maturity (Plate IV., fig. 5), and under-
goes no further change. In the female a considerable
lengthening of the genital segment accompanies the
appearance of the various appendages. Fertilisation next
takes place; then the young female severs its connection

* Development of the embryo and metamorphoses of Lernwa branchia-
lis. Trad. Soc. Imp. des Naturalistes de St. Petersbourg, vol. xxvi.,
livr. 4, No. 7, Sect. de Zool. et de Physiologie, 1898, in Russian, with
German resume.

106

with the chitinous filament, and leads a pelagic life (Plate
IV., fig. 4. Nat. size 23 mm.). This condition is fre-
quently found in collections of plankton, and unless care
be taken may readily be confused with immature stages
of allied forms. I. C. Thompson, F.L.S.,+ was the first to
recognise certain copepods taken in collections of plank-
ton from Liverpool Bay, &c., as the young of Lernea, from
Claus’ figures. The presence of the males of Lernewa in
plankton is to some extent accidental, as only the females
lead a pelagic life. The males remain on the gills after
the females have gone. The result of the examination
of the contents of a fine filter, through which the waste
water was passed from the tanks containing flounders in
the Piel Hatchery, showed that females were always more
numerous than males. The ratio, after a number of
trials, was found to be one male to twenty-five females.
At the conclusion of the pelagic life the young Lernwa
again fixes itself to the gills of a fish, and the retrogres-
sive metamorphosis commences. The parasite buries its
cephalo-thorax into the tissues. This region then
develops into horns, which are situated one at each side
and one dorsal. These pass out at right angles to the
body into the tissues of the host. At first they are simple,
but by gradual division in each horn they acquire the
characters found in the adult (Plate V., fig. 8). The
anterior part of the segment curves over, taking up the
position shown on Plate V., fig. 4. The eyes, antennules,
antenne, mandibles and maxille disappear, leaving only
the first maxillipedes, which are represented by small
hooks in the adult. The free thoracic segments fuse, but
the feet remain as in the cyclops stage. The genital
segment elongates until fully fifteen times the original

+ Revised Report on L.M.B.C. Copepoda. Trans. L’pool Biol. Soc.,
vol, vii., p. 212.

LOT

length. The abdomen only lengthens a very little. The
elongation takes place during the development of the
horns and before the eyes and the other organs disappear.
This condition is shown on Plate LV., fig. 6; the nat.
size is ll’"4 mm. The next phase, represented on Plate
IV ., fig. 7. shows that the development of the horns, the
disappearance of various. appendages, and the great
lengthening of the genital segment is followed by a loop-
ing of the posterior region of the latter. This loop
eradually expands, and finally takes on the adult
condition.

In the metamorphosis of the cephalo-thorax the ovaries
are thrust into the genital segment, and take up a position
on the dorsal aspect of the posterior region of that seg-
ment, in such a manner that the more anteriorly placed
portion of the ovary in the adult is what was the posterior
part in the cyclops stage (see Plate V., figs. 1 and 4).

The cyclops stage of Lernea was first found in setu by

a8

Metzger,* who published a short note on the observations
made and the conclusions arrived at early in 1868.
Claust later on in the same year, from specimens supplied
by Metzger and fresh material, confirmed the observations

of that Zoologist.
ConcLUDING REMARKS.

In the account set forth on the above pages, it will be
seen that there are remarkable differences between the
changes that take place in the hfe history of the two cope-
pods before they reach maturity. In the one case
(Lepeophtheirus) the lite history exhibits a series of pro-
gressive developments. In the other (Lernwa), although

* Ueber das Mannchen u. Weibchen der Gattung Lernaa, vor dem
Hintritt der sog. riickschreitenden Metamorphose. Jany., 1868.

+ Beobachtungen ueber Leriwocera, Peniculus, und Lernea, 1868.

108

for a time it advances, yet after a particular period has
arrived the remainder of its development is retrogressive.
The various appendages in each parasite are developed in
the same order. In the one they become perfected when
the creature is fully developed. In the other, long before
the animal has reached maturity some have disappeared,
the remainder continue in a rudimentary condition, and
it is incapable of further movement. The internal organs
of both copepods are developed in the same way. In one
they continue advancing until perfected, and the animal
is thus capable of living for considerable periods apart
from its host. In the other, such organs as the digestive
gland, the brain and nerves, and the blood system become
rudimentary, if they do not altogether disappear. The
ovary loses its original position and passes into the genital
segment. The animal dies when removed from its host.
If only the adults were known, it would practically be
impossible to recognise that such a form as Lern@a was im
any way related to such a typical free-swimming Copepod
as Calanus, and it would therefore still occupy
an uncertain position. But when the whole life
history of both copepods is known, tracing the connection
becomes comparatively easy. Both originate from a free
larval stage known as the nauplius, which has been
regarded as the representative of a far back common
ancestor. Both pass through a cyclops stage. The
one ancestral cyclops form, we may suppose, by maintain-
ing a free swimming life, gradually acquired more perfect
appendages, and became at last the form now known as
Calanus. The other cyclops form by adopting a sedentary
life, and depending on other animals for its food, became
semi-parasitic like many of the ascidian- and sponge-fre-
quenting forms of copepoda. ‘The transition from
Lichomolgus-like copepods to such forms as Bomolochus

109

and Mrgasilus became simple. Further change in form
and habit continued as the various appendages, through
constant rest, degenerated. ‘The animal became in con-
sequence more and more dependent on its host for food.
Such changes extending over a long period of time,
have apparently resulted in such a form as Lernea,

Some Zoologists divide the fish parasites into blood-
suckers and mucus-eaters, on account of the apparent
presence or absence of blood in the alimentary canal. It
is doubtful if such a division is really satisfactory. The
probability is that they are all blood-suckers in different
degree, and that the presence of blood is only obvious
because certain organs are absent. Lamargus muricatus,
one of the Caligida, appears to make excavations into the
skin of its host, Orthagoriscus mola (the short sun-fish).
Several individuals are usually found in each excavation.*
No obvious appearance of blood can be observed even in
these parasites.

One or two parasites on a fish may not be hurtful, but
when the numbers increase they probably have an irri-
tating effect, and finally, when they remain in one position
for some time, the skin and tissues become lacerated.
Consequently even such external parasites as have been
regarded as harmless mucus-eaters may really have an
injurious effect upon the fish.

There is much opportunity for investigating the
internal structures of the various families of fish parasites.
The most of the literature hitherto published deals with
the external characters only.

The specimens necessary for the work connected with
this memoir have been almost entirely collected from fish
caught in the vicinity of Piel. The author is indebted to
Mr. R. Newsham, Jun., the Laboratory Assistant at Piel,

* A, Scott. Trans. Nat. Hist. Soc., Glasgow, vol. iil., part 3, p. 266. 1892.

110

for help in collecting. The important stage of Lernea,
shown on Plate IV., fig. 6, is drawn from a specimen sent
by Mr. T. Scott, F.L.S., the author’s father. It was
found on the gills of a whiting caught in the Bay of Nigg,
Aberdeen, in 1900, and was the only one met with in the

course of these investigations.

EXPLANATION OF PuaTEs.

Reference Letters.

a. antennule.

a antenna.

av. lateral frontal sucker.
an, anus.

b. median frontal sucker.
bls. blood space.

c. filament duct.

cg. filament gland.

cn. chitin.

D. dorsal.

d. opening of spermatophore.
e. eyes.

y. filament.

. ganglia.

gl. gland.

SQ

2. intestine.

K* left anchor process.
K? median ,,

K® right +

L. left.

ld. duct of digestive gland.
Ins. lens.

ly. digestive gland.

M. mouth.

m. mandible.

ml. muscle.

ml.a. antennule muscles.

ml.an. anal muscles.

ml.f. frontal muscles.

ml... intestine muscles.

ml.l. lateral muscles.

ml.m. mandible muscles.

ml.maep. first maxillipede
muscles.

ml.pt. posterior cephalic
muscles.

ml7rt. rectum muscles.

ml.st. stomach muscles.

max. first maxilla.

max second ,,

map. first maxillipede.

mexp* second ,,

nm. nerves.

ne. nucleus.

O. ovary.

od. oviduct.

@. oesophagus.

og. optic lobe.

om. muscles of the oviduct.

os. ovisacs.

ov. ova.

p’ first pair of feet.
pi second “5

pe third i
p fourth >
p” fifth A
pg. pigment.
R. right.

7. rostrum.

rep. receptaculum seminis.

rt. rectum.

rin. retina.

ry. fin ray.

S. spermatozoa.

sbg. subcesophageal
ganglion.

sf. sternal fork.

sg. cement gland.

sp. spermatophore.

spg. supra-cesophageal
ganglion.

st. stomach.

t. testis.

V. ventral.

va, vagina.

ud. vas deferens.

vu. vulva.

y. opening of digestive duct

into the stomach.

z. pore canals.

Nos. 1 to 18 nerves, as
follows :—

1. optic.

2. antennules.

3. antenne.

4, mandibles.

4a. lateral frontal margins.

4b. first maxille.

d. second maxille.

5a. lateral cephalic muscles.

6. first maxillipedes.

7. second maxillipedes.

8. first feet.

8a. stomach muscles.

9. second feet.

9a. posterior cephalic

muscles.

10. third feet.

11. fourth feet.

12. abdomen.

13. fifth feet.

Puate I.

Fig. 1. Lepeophtheirus pectoralis, mature female, dorsal

view. ™ 17.

Fig. 2. Lepeophtheirus pectoralis, mature male, dorsal

view. xX 17.

Fig. 38. Lepeophtheirus pectoralis, nauplus stage, newly

hatched.

Fig.

6.

~T

jew)

6.

10.

112

Lepeophtheirus pectoralis, “ chalimus”’ stage.
x 26.

Caligus rapax, early “‘chalimus” stage attached
to fin ray of young cod, the line d’e' represents
the surface of the skin. X 54°4.

Caligus rapax, “chalimus”’ stage, previous to
throwing off the filament attachment. On tail
of young lumpsucker. xX 15°24.

Caligus rapax, mature, part of the frontal plate
showing a lateral sucker. x 22.

Pirate IT.

Lepeophtheirus pectoralis.

Female, ventral view, showing the various
appendages and their muscles. x 17.
Female, dorsal view, showing the chief muscles
and blood currents. ‘The arrows indicate the
course of the blood. x 17.

Female, ventral view, showing the digestive
gland, its duct and alimentary canal. x 17.
Female, ventral view, showing the reproduc-

tive organs. x 17.

' Male, ventral view, showing the reproductive

organs. x 26.

Genital segment and abdomen of an immature
female, ventral view, showing vulva (vw.). x 40.
Spermatophores detached from genital openings
of a female. x 206.

Mouth from the anterior base, with the
mandibles inside, showing the muscles and
ducts of digestive gland. x 28.

Digestive gland. x 77.

Longitudinal section of the ovary. x 40.

Fig.

~~

6.

10.

le

118

Transverse section of pore-canal at the base
of the mouth. x 590.

Prate IIT.
Le peo phtheirus pectoralis.
Female, ventral view, showing the nervous
system in setu. x 17.

The nervous system from the ventral aspect.

Female, nearly median longitudinal section.
x UT.

One of the antennules, showing the nerve
endings. x 76.

Median longitudinal section of the ganglha,
showing the “pinhole” cesophagus passing
through between the supra and sub-cesophageal
parts. x 77.

Transverse section in the region of the eyes.
x 38.

Transverse section in the region of the supra-
and sub-cesophageal ganglia. x 39.

Transverse section in the region of the second
maxillipedes. x 30.

Transverse section through the genital segment,
female. x 30.

Transverse section through the genital segment,
male. x 38.

Part of a transverse section of the intestine.
x 76.

Horizontal section of the dorsal aspect of the
supra-cesophageal ganglion, showing the cross-
ing of the fibres of the optic nerves. x 152.

Transverse section of the eyes. x 152.

Fig.

114
Prats IV.
Lernea branchialis.
Mature female, from the right side. The line
f’ g' shows how much of the anterior portion
is buried in the branchial arch. x 4°5.
Nauplius stage, newly hatched. x 50°8.

Very young female, unfertilised, dorsal view.

From gills of flounder. x 515.

Fertilised female, dorsal view. Just after
leaving the gills of flounder. x 27°6.

Mature male, dorsal view. From gills of
flounder. x 28°5.

Fertilised female, ‘* Penella” stage, dorsal view.
Just after settling on gills of Gadus (whiting).
x 15°5.

Later stage than Fig. 6, from the left side.
The folding has just finished. Nat. size.

Apex of gill filament of flounder, showing mal-
formation caused by the young Lernea. x 18°6.

Apex of gill filament of flounder, normal. x 18°6,

Puate V.
Lernea branehialis.
Fertilised female, ventral view, showing the
appendages, the reproductive organs, and
nervous system. x 47°6.

Nearly median longitudinal section of the same.
x 47°6. .
Transverse section in the region of the eyes.

x 80.

Mature female, from the right side, showing
the first maxillipede and the four pairs of feet,
the alimentary canal and the reproductive

Fig.

Fig.

Fig.

Fig.

115

organs. The specimen was cleared in xylol,
and the right anchor process removed. x 4.
Transverse section through « £8, (Fig. 4,)
showing the museular wall, the ovary,
oviduct, cement gland, and intestine. x 9.
Transverse section through « @, (Fig. 4,) just
anterior to the rectum. X 20.
Portion of the cement gland. x 20.
Front view of the anchor processes of an adult
female. x 4,

Taste I.—Abstract of the results of Hauls with a Shrimp
(Area A) during the

Average

SHRIMPS.

Trawl made on the Burbo Bank Shrimping Ground

period 1893—1899.

PLAICE.

Soues.

Dass.

WHITING

oyu Number) Total Nos.) ° Nos F Su RIMPS. “Average Nos. PLAICE. Average SoLns. Average Ds et Average Watt ING.) Ayers ge
ATE. of of ae Total Nos. =) otal : : otal = Total = otal = ar
jefraeily. hh. of Fish SPoatte of quarts | Wanbers. | Numbers NnEA eRe: Numbers Namba Numbers Numbers. Numbers
per haul. | "| perthaul: |= per haul. per haul. per haul. per haul.
1893—May 4 1005 251 164 4 742 185 28 7 127 32 69 17
June 4 5948 1489 38 gh 1868 467 48 12 3304 526 965 241
August 3 8165 2722 61 204 1810 603 109 36 2276 758 3850, 1283
September 5 19593 BOL) 78 15°6 14548 2910 173 35 2115 425 2480 496
October ... 1 662 662 07125 0-125 280 280 2 2 241 241 53. 53
November 2 866 433 2:25 1-125 170 85 2 1 536 268 130 65
December 2 621 310 10 5 162 | 81 ) O 426 213 18 9
1894—January ... 2 1235 617 14 uf 492 246 15 i) 531 265 165 82
February 4 1792 448 16 699 175 20 5 746 186 266 66
March 5 5237 1047 48 96 1474 295 301 60 2084 417 1101 220
April 4 3922 980 30°5 76 1067 267 83 21 2379 595 524 131
May 4 5376 1344 26°75 67 2010 502 82 20°5 : 636 571 143
June 9 6599 733 TO5 8-5 2932 326 318 35 293 227 25
July 3 3838 1279 24:5 8-1 461 153 69 23 : 327 2160 720
August 6 21913 3652 62°5 10-4 3329 555 95 16 10801 1800 7493 1249
September 4 8111 2028 133 3352 2283 571 39 9 1288 321 4014 1003
q October ... 3 3682 1227 130 43°3 680, 226 28 9 1410 470 1561 520
= = cE = =
1895—March 2 53 26 0-5 0-25 40 20 0) 0) 0 0) 0) 0)
April 3 734 245 18 6 170 56 4 1°3 306 102 237 79
May 8 3671 459 102°5 13 571 | 71 158 20 1977 247 683 85
June 4 3575 894 50 12°5 272 68 29 Ti 2765 691 302 75
July 5 19245 3849 136 27 3104 | 621 129 26 5117 1023 9500 1900
August 3 8750 2916 22 73 982 527 63 21 1621 540 5272 1757
September 1 4404 4404 7 U 2315 2315 5 5 705 705 1224 1224
October ... 3 S897 2965 25°5 8:5 1747 582 O 0 3003 1001 2434 B11
November il 1000 1000 9 9 284 284 0 0 345 345 292 292
December 1 385 385 6 6 4 62 62 0 0 193 193 (le | 71
1896— March 2 1911 955 12 6 954 477 5 2°5 546 273 258 129
April 2 2819 1409 5 Dy 1258 629 13 65 626 313 741 370
May 2 1481 740 10°5 5°25 649 524 a) 2°5 498 249 294 147
June 3 4199 1399 13 4:3 1703 568 29 10 1963 654 361 120
July 2 6996 3498 8:5 4°25 2219 1109 49 25 1169 584 3534 1767
August il 2608 2608 O75 O75 206 206, 1 1 981 981 1433 1433
September 1 723 723 8 8 120 120 57 57 150 150 298 298
October ... 3 2920 973 92 30-6 397 132 128 43 1534 511 800 266
1897—February 1 446 446 a3) 1°5 94 94 34 34 96 96 | 215 215
April 2 490 245 25 1:25 190 95 66 33 88 44 | 257 128
August 1 1913 1913 2°5 25 1278 1278 197 197 287 287 150 150
September 2 2591 1295 5°5 2°75 685 342 62 31 658 329 1186 593
October ... 1 1228 1228 7 7 111 111 58 58 756 756 252 252
1898—July 4 5464 1366 41 10°2 1175 294 1060 265 16258 407 1352 338
August 3 4226 1409 16 5'3 166 55 341 114 1678 559 1967 656
September if 20330 2904 57-5 8:2 1316 188 979 | 140 8374 1196 9677 1382
October ... 2 4686 2343 7 35 625 312 254 127 1071 535 2676 1338
1899—June 6 1308 218 60 10 112 18 223, 37 718 119 94 16
July 1 201 201 / Ti 30 30 43 43 3 3 71 71
August 15 31718 2114 292 20 2951 197 2361 158 $340 556 17608 1174
September 2 2133 1066 39 19°5 190 95 209. 104 982 491 654 327
October ... 4 1237 309 23 a7 79 20 236 59 829 207 933 233

. oe

clei

_

Taste H.—Abstract of the results of Hauls with a Shrimp
Channels (Area B) during the period 1893—1899.

|

Dass.
Total

number.

| WHITING.
Total
number.

= ;. | Average MPS. a PLAICE.
oe | per haul. | of quarts. | numbers.
|
1893. | |
April . 5 1019 204 13 | 2°6 378
May....... 1 312 312 0-5 Oo 283
August 3° 7065 | 2355 | 48 | 1 13
September YT | (425 coy Ie 7 321
October:.....:...: 5 | 3739 748 } 36 Xi 1846
November ...... 2 1054 527 8 4 843
December ...... 4 2933 | 733 1-75 0: 1591
1894. |
January ......... | al 5310 | 483 45 3400
February 1 669 | 669 0-125 | 530
March.... 1 647 647 0-125 | 284
3 430 148 12 166
1 257 | 257 4-25 212
1 753 753 13 367
1 132 USP a} 6:5 61
1 394 394} 6 201
| —|
2 1141 570 15 0-75 328
1 12) | 12 10) 0 0
2 758 | 379 15 75 62
3 399 | 138 | 105 3:5 26
2 3946 | 1973 12 6 674
1 466 | 466 2 2 166
1 666 | 666 | 22 22 52
November 2 4591 2995 | tS} | 4 1135
al = |
1896. |
January ......... 2 3830 1915 | 1 2393
February : 1 591 591 0-5 365
UNION gstaccecase=e] 1 ge Li 4 6
| ae at
1897.
WMarehie. cesses: 1 213 213 1 129
IMB eceosonced 1 243 248 | Od 158
1898. |
January ......... 2 2749 1374 alt 1772
Oye esas ee 2 1344 672 8 933
September me 417 417 | 18 18
November 2 | 2350 1175 | 60 410
December ...... il | 724 724 | 16 174
1 | 167 167 2 62
4 3851 963 | 106°5 413
uf 2977 425 198 622
4 1100 275 | 202 266

Trawl made in the Horse, Rock, Queen's and Crosby

WHITING.
Average

No. per

1280
7
161
17

338
2767

Flounders
and Cod
only.

| 1381
ay

Praticr. .
Average SOLES
Noupaue| Total
No. per Lag
haul, | Zumber.
=
76 92
283 14
4 14
321 29
369 22
421 2
398 0
310 0
530 0
284 0
55 109
212 15
367 55
61 3
201 0
164 0
0 0
31 0
8 2
337 87
166 \) peat
52 0
567 0
1196 0
365 0
6 0
129 34
158 50
886 99
466 352
18 108
205 628
174 240
62 95
103 84
89 258
66 44

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Taste V.—Showing the ratio of Immature Fishes to
Shrimps in the average monthly catches (Tables III.
and IY.) taken on the Mersey Shrimping Grounds :—

AREA A. AREA B.

be ae | SOLEs. | PLAICE. | WHITING. | Sones. | PLAICE. | WHITING.
~~", | per Qt. | per Qt.| per Qt. | per Qt. | per Qt. | per Qt.
| Shrimps Shrimps) Shrimps. Shrimps|Shrimps.’ Shrimps.

January esl 35-1 11:8 Lf | S49 5
February 31 45°3 27-5 0) 1432 48°3
March Spal 40:8 22-4 30-2 B67 12-7
April 3:0 47°9 B14 2°5 20-9 ily
May ASF 25°5 O35 ye ose: 20°7 13
dnmaey see aaa) | ET 29 8:2 4-7 22°6 0-8
July | 6:2 32-2 (Als) | 19°3 61-9 8:3
August... ...| 6°9 23°5 82-7 | 0-6 3-1 43-7
September 4:6 65-4 59-5 1:8 5 5
October... 2-4 13°8 341 0-3 8:3 4-6
November O-2 40-4 37-6 8:3 31:4 | )
December 0) 14 a) 10-0 81:9 | 5

Taste VI.—Shewing the Average Hauls made with a
Shrimp Trawl during the 8rd quarters of the years 1893
1899 on the Burbo Bank Shrimping Ground (Area A) :—

th aa] | | | |
L < n a | el : oo par Nanos:
; oo Se 2 S| | = ap| g| al = la 2
Deke: C4) B85 |8S| 84 [Seledlad| ad lgzlee 82
Ss) a5 ge| 25 Belssclss zties Es
A2sa\|n SF At! Me AatMelna| Oe Galea b=
| | |
1893—3rd quarter...; 8 | 139 17 (16358 2045) 282) 35 | 4391 | 549' 6330 | 791
1894— 3rd quarter...| 13 | 220 (17 6073 | 467) 203) 16 13067 |1005 13667 1051
1s9—Srquater. revel NCS (18 6401 | 711] 197| 22 | 7443 | 827|15996 |1777
1896—3rd quarter...| 4 | 17-25 | 4:3) 2545 | 636) 107| 27 | 2300 | 575] 5265 |1316
1897—3rd quarter...) 3| 8 2-6 1963 | 654] 259) 86 | 945 | 315 1336 | 445
1898 —3rd quarter...| 14 | 114°5 8 2657 | 190.238C'170 11680 | 834 12996 | 928
1899-—3rd quarter...| 18 | 338 19 3171 | 1762615/145 | 9325 | 518 18333 1018
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