SCIENTIFIC SUMMAEY. 
265 
The Metamorphosis of the Ostracoda. — Dr. C. Claus has given the results of 
some interesting observations in a late number of Siebold and Kollicker’s 
Zeitschrift. The species which has been particularly investigated is the 
Cypris ovum, upon the young forms of which he writes. His conclusions are: 
— (1.) That the Ostracoda pass through a sort of metamorphosis, for their shell 
varies in form, and they only acquire their limbs by gradual development. 
(2.) The youngest stages are shells bearing Nauplius forms , with three pairs 
of limbs for movement, — viz., two antennae and the mandibular appendage. 
(3.) There are altogether nine stages of C. ovum , which are successive, and 
may be distinguished from each other, and of which the last represents the 
sexually -mature condition. (4.) These stages of development are marked by 
the stripping off of the skin ; there are therefore eight corresponding moults. 
(5.) The mandibles arise first in the second stage, as powerful jaw-prolonga- 
tions at the basal joint of the mandibular foot. (6.) Only the hinder antennae 
already possess at the youngest age the complete jointing and figure of the 
sexually-mature animal. (7.) In the second stage the anterior maxillae and 
anterior feet, except the antennae and mandibles, are attached. (8.) The 
maxillae of the second pair originate first in the third stage, consequently 
later than the following pair of jointed bodies, distinguished as the first foot. 
(9.) The maxillae of both pairs and the hinder foot present in their first ap- 
pearance a nearly corresponding form as a triangular plate running out into a 
little hook. (10.) The anterior feet proceed from the top to the base in their 
jointing. (11.) The abdomen gives rise to two long furcal joints. — Yide 
The Quarterly Journal of Microscopical Science. 
Fissiparous Beproduciio’n in Anthea cereus. — In the last number of the 
Dublin Quarterly J ournal of Science, Dr. E. H. Bennet describes the process 
of fissiparous division in one of the above species. Although there is 
nothing fery novel in the phenomenon witnessed by Dr. Bennet, his essay is 
of importance from the fact that many persons are disposed to think that 
true multiplication by division does not occur in the Anthea. Although Dr. 
Bennet’s observations did. not extend to an anatomical examination of the 
individuals produced by fission, they go quite far enough, however, to prove 
that division was completed, and that the two halves lived as independent 
animals for a few days. The whole time which the division took from the 
first observation of the opening in the base to the complete separation of the 
halves, was barely three hours. The exciting cause of the process seems to 
have been the condition of the water in the vessel, just verging on decomposi- 
tion. The most important part of the observation is the mode of the division. 
This began by a fissure in the base, and proceeded in the manner described so 
well by the author in the following passage : — “ It is a curious fact that the 
tentacles corresponding to the two parts now contracted separately ; hitherto 
the contractions were convulsive, and set in suddenly at intervals and all 
together, now there was a distinct pause between the convulsion of the upper 
and lower divisions, the upper always preceding the lower by a few seconds. 
Does not this suggest that the seat of the central nervous system of Actinia 
occupies the base, as Spix thought he had demonstrated — although this 
demonstration has been rejected by every authority who has followed him ? 
At 5.10 the walls of the stomach could be seen strained across the fissure, 
and they presently gave way, the rent extending right through the column to 
YOL. Y. NO. XIX. T 
