438 REPORT—1899. 
The Rearing of Larve of Echinide. By Professor E. W. MacBripr. 
The problem which engaged my attention during the spring of 1898, 
when I occupied the Cambridge University Table, and during the present 
summer, when I held the Table belonging to this Association, was the 
rearing of the larve of echinoderms. Since the work done this year was 
only the completion of that commenced in 1898, the results of the two 
years may be considered together. The primary object which I had in 
view was the collection of sufficient material to enable me to undertake a 
thorough investigation of the formation of the organs in the Echinide, 
along similar lines to the researches already published on the development 
of Asterina gibbosa. The object was accomplished this summer in the 
case of one species, viz. Hchinus esculentus ; but as it will be some con- 
siderable time before the material can be worked up, I shall content my- 
self with mentioning some points of general interest in connection with 
the rearing, since these may throw some light on the problem of the rear- 
ing of the eggs of marine animals in general. 
So far as I am aware, the larve of the Echinide have heretofore been 
successfully reared only by two people, viz. Théel and Bury. Théel has 
already published his method, and the results of his work, so far as 
Echinocyamus pusillus is concerned ; he has also told me that he has 
reared Echinus miliaris. Bury informed me some time ago that he 
had reared a few plutei of one of the Neapolitan species through the 
metamorphosis ; but he experimented—to judge from his description— 
with only very few at a time. 
Dr. Dohrn informed me that unsuccessful attempts had been made at 
Naples to keep larve living until they had metamorphosed by following 
Théel’s directions ; it may therefore be inferred that these directions have 
not fully described the difficulties which crop up in the course of the 
experiment. 
There are three species of Echinus commonly found in Plymouth, viz., 
£. miliaris, E. esculentus, and £. acutus. The last two in colour and 
size closely resemble one another ; 2. acutws has, however, longer and 
sparser spines than Z. esculentus ; it is not so commonly found, and Mr. 
Allen informs me that it is an inhabitant of deeper water. 2. miliaris, 
on the other hand, does not attain more than half the size of the other 
two species, and its predominantly green colour serves at once to dis- 
tinguish it from them. 
The eggs of £. miliaris and £. acutus are about the same size; that of 
E. esculentus is about double the size of either, and it was for this reason 
especially that I selected the last species as the most suitable. The size 
of the egg is, of course, conditioned by the amount of yolk ; and the 
greater the amount of yolk, the greater, so to speak, is the initial velocity 
with which the development is launched : the longer the time before the 
larve has to depend exclusively on its own exertions for food. 
Experiments were made also with 2. miliaris and #. acutus ; the 
larve of Z. miliaris is strikingly different at all stages of development 
from that of ZF. escwlentus, and in a forthcoming paper in the ‘Quarterly 
Journal of Microscopical Science’ these differences will be detailed. I 
only succeeded in rearing the larve of /. acwtas for the first ten days of its 
existence, and during this time it strikingly resembled that of Z. escw- 
lentus, but was in correspondence with the smaller size of the egg of about 
half the size of the larve of Z. esculentus, 
