1885.] 



CLADOCERA. 



8 



as scarcely to admit of being broken except with a hammer. 

 In water, on the other hand, it dissolved with comparative facil- 

 ity, the separate portions breaking up into numerous fragments 

 and ultimately resolving into a finely dispersed muddy deposit, 

 which at first gave to the water a very dark, cloudy appearance. 



My first attempts to dissolve a portion of the mud in water 

 at once convinced me, that it actually contained so-called win- 

 ter-eggs of Cladocera; and more especially one kind of such 

 ova, or rather their envelopes, was very frequently caught sight 

 of and easily observed, by reason of their floating up to the 

 surface on stirring about the mud. It was not difficult to recog- 

 nize at a glance in these corpuscles the so-called ephippia of a 

 species of Daphnia, each (see Pl. 1, figs. 1, 2) exhibiting the 

 aspect of a diminutive pod, with two obliquely disposed recep- 

 tacles for as many germs, or ova. Moreover, I could distinguish 

 4 other different kinds of ephippia, occurring however much 

 more sparingly, one of which (fig. 11), like the aforesaid kind, 

 with 2 egg-chambers, whereas the other 3 had a single chamber 

 only. One of the latter (fig. 12) exhibited a form and struc- 

 ture readily determinable as the ephippium of a species of 

 Simocephalns ; the other two (fig. 13 & 14) I have found, by 

 subsequent experiments in hatching, to be, respectively, the 

 ephippia of a Gerio daphnia and a Moina. Exclusive of the 

 above-mentioned ephippia, occurred a considerable number of so- 

 called statoblasts or winter-germs, of 2 different kinds of Bnjozoa, 

 one of which — apparently a Plumatella — was successfully 

 hatched in the course of the summer. 



In the beginning of May, when I thought the temperature 

 was so far advanced as to admit of commencing the hatching 

 operations, I portioned out some of the dried mud in small 

 glass jars, pouring over it ordinary spring water. With a view 

 to accelerate the hatching, I placed the jars, whenever pos- 

 sible, so as to expose them directly to the rays of the sun; 

 but, owing to the situation of my laboratory, this was confined 

 to a few hours only in the fore-noon. On examining from time 

 to time the ephippia floating in the glass jars, I found in some 



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