6 Ech. 
ECHINODERMATA. 
before and after fecundation were made on ova of Toxopneustes liridas^ 
but have, probably, as shown in the critical chapters of his essay, a 
general bearing on the subject. Before fecundation, the “ germinal 
vesicle’’ migrates towards the periphery of the egg, and vanishes, leaving 
behind only the “ germinal spot ” as the future nucleus of the egg. 
After fecundation, a small nucleolar body (probably the head of a sper- 
matozoon) makes its appearance in the interior of the egg, near the 
periphery ; it exercises a certain attraction on the protoplasm, which 
results in a radial arrangement of the granules around a clear space 
surrounding the spermatic (?) nucleolus ; this slowly advances towards 
the centre of the egg, where it is met by the nucleus advancing from 
the other side. A juxtaposition, and finally conjugation and con- 
fluence of these opposite elements takes place, and the first “ nucleus of 
segmentation ” is thus formed. The first division of the egg is now pre- 
ceded by a stretching and subsequent division of this nucleus, and by the 
development of clear spaces, forming new centres of radiation for the 
protoplasm, at its extremities ; and similar proceedings are repeated each 
time a new segmentation takes place. These manifestations of the proto- 
plasmic yelk-segments are evidently governed by those of their nuclei 
which act as the automatic centres of the cells. [Compare the critical 
remarks of Butsciili, Abh. senck. Ges. x. pp. 432-438 ; and of E. v. 
Ben EDEN, on the germinal vesicle, &c. : Q. J. Micr. Sci. (2) xvi. 
pp. 153-182, and Bull. Ac. Belg. (2) Ixi.] 
Some paragraphs of Greeef’s short preliminary notes on the anatomy 
and evolution of Echinoderms (7) are devoted to the evolution of 
Asterias rubens. Several details brought forward by Hertwig, Selenka, 
van Beneden, and others, in other sub-classes, are here indirectly con- 
firmed. Greeff, however, has not seen anything corresponding with 
Hertwig’s “ spermatic nucleolus ” and its conjugation with the nucleus; 
on the other hand, he has observed the “ globule of direction,” preceding 
or succeeding the first division of the egg, and he is inclined to believe 
that the “ germinal spot ” disappears completely after having assumed a 
fixed granular character. It may also be noted that J. Muller’s “ Bipin- 
naria and Brachiolaria of Elseneur” are both referable to Asterias 
rubens, which is sexually matured in spring (April and May). His asser- 
tion that non-fecundated eggs are capable of evolution parthenogeneti- 
cally, at least as far as the stage of the ciliated (?as<r«7a-larva, is very 
remarkable The evolution of the non-fecundated eggs, however, is much 
slower than the normal one 
Anatomy of Holothuriidce. Teuscher (20) has studied several points of 
the more delicate anatomy and histology, especially of H. tubulosa. As in 
all Echinoderms, there is one aquiferous and two distinct sanguiniferous 
vascular systems, without any mutual communications, in the Holo- 
thuriidoi. Each of the large ambulacral water- vessels is separated from 
the nervous trunk, situated outside and alongside of it, through a blood- 
vessel of the neuro-dermal system ; a nerve and a branch from the blood- 
vessel go with each branch of the ambulacral water- vessel to the feet or 
suckers. The nerve-trunks and neuro-dermal vascular stems also go 
together to the pharynx, whore their ring-like connecting parts are like- 
