Prof. E,. Kossmann on the Cryptoniscidse. 11 



a brood-space with a transverse entrance-fissure is formed by 

 invagination, and as its inner surface is the former surface of 

 the animal in the neighbourhood of the oviducal aperture, the 

 oviducts of course no longer open outwards, but into this 

 newly-formed brood-space. 



Somewhat more complicated, but perhaps more primitive, 

 is the arrangement in the other Cryptoniscidaj, at least in 

 Cryptoniscus and Liriopsis. Fraisse* falls into an error, 

 which, however, his predecessor had escaped ; he says, " This 

 brood-cavity was previously present, for it is simply the body- 

 cavity," and adds, " How the ova get into it I cannot say ;" 

 and, in fact, it would be hardly possible to establish a con- 

 ceivable hypothesis upon this view : deposition of the ova in 

 the body- cavity would be something unheard of among Crus- 

 tacea. Into this brood- or, according to Fraisse, body-cavity 

 lead two " respiratory " apertures, already very fully de- 

 scribed by him, one of them in the neighbourhood of the mouth, 

 the other further back, and the two united with each other by 

 a longitudinal groove (upon the ventral surface). Of this 

 groove Fraisse says (p. V6) : — " When the larvae are ready for 

 a free existence, a fissure bursts which formed between the 

 tsvo respiratory apertures during the third stage, and was 

 previously covered and closed by a thin cuticular layer." 

 Through this the larvae are set free. 



The actual course of events, as I have ascertained by the 

 study of numerous transversely-sectioned specimens, is as 

 follows. Here also, first of all, the two oviducts (which 

 Fraisse, /. c. p. 9, was unable to detect) open on the ventral 

 outer surface of the body. Their originally circular aperture 

 becomes elliptical and is soon drawn out before and behind 

 into a shallow groove, so that we may easily recognize two 

 such parallel longitudinal grooves in the female when not yet 

 quite mature. Now the wall between the two grooves begins 

 to sink in, and thus we obtain, instead of the two shallow 

 grooves, an elongated depression, the two side walls of which 

 curve into one another before and behind. These side-margins 

 now, however, grow towards one another until they touch 

 throughout nearly their whole length ; there remains conse- 

 quently only a hair-like slit, which passes at its posterior and 

 anterior ends into a rounded hole, and these two holes lead 

 into a cavity formed by the sinking in of the wall lying be- 

 tween the two genital furrows. This cavity, into which of 

 course the oviducts open, is the brood-cavity, but it has abso- 

 lutely nothing to do with the body-cavity. It becomes tilled 



* Fraist<c, /(>('. cif. \\. 12. 



