On Stenocypris Chevreuxi. 21 



filled with an opaque orange matter, the nutritive yolk, 

 and are now nearly ripe. They are successively received 

 into the egg-cavities of the body, and there often accu- 

 mulate in rather large numbers, being at intervals expelled 

 through the genital openings. All the ova contained in the 

 said egg-cavities are of exactly the same size and in the same 

 stage of development; and these cavities cannot therefore pro- 

 perly be regarded as a part of the ovaria themselves, but only 

 as a sort of reservoir for the eggs. They are still only 

 surrounded with a very thin, pellucid, vitelline membrane, 

 without any trace of the strong, coriaceous capsule, which 

 is found enveloping the deposited ova. This capsule 

 must accordingly be formed immediately after the ova have 

 passed through the genital openings. 



Biological Observations. 



At first only some few specimens of this form made 

 their appearance in one of my aquaria rather late in the 

 autumn. They thrived very well, and soon reached maturity, 

 whereupon they began to deposit their eggs in small clusters, 

 chiefly on pieces of weed contained in the mud. The eggs 

 after some time developed into young ones, which in their turn 

 became adult, and in the same parthenogenetical manner 

 as the first hatched specimens, gave origin to a third 

 generation. The aquarium contained this Ostracod during 

 the whole winter, and though from time to time a con- 

 siderable number of specimens were taken out aud pre- 

 served, some specimens yet remain in the aquarium. All 

 specimens, without exception, were of the female sex, and 

 I do not doubt therefore, that this form, like several of 

 its allies, is exclusively partenogenetical in character. 



