356 r\(;K sko(;shkh(; 



All tlu'se lai'li! strongly .support tlu- i-urroi'tiif.ss ol tln' aljovr-ipioli'd liypolhosi.s [)Ut 

 forward by G. \V. MCi.lkm in 1898 as to the reproductive opc'()lop;y of this si)ecies.* 



According to this liypothosis the specimens of the tirst to the lourtii (ulunins of the jlmvc 

 table probably arc to be interprett'd in llic lullowiug way: 



1) The females of the fourth cohinin represent specimens wliich have either not yet 

 had their planktonic period, in other wonis have not yet l)een fertilized or else have just 

 finished it. 



2) The females in the third toluinu are somewhat older; they Jiave just definitely 

 returned to a life of creeping and digging in the mud of tlie l)ottoin owing to the breaking 

 off of their natatory bristles on the second antennae. 



3) The females in the second column are still older; eggs had been pressed out into 

 their brood chambers for further development there. 



4) The females in the first column are the oldest; their brood chambers hud just been 

 emptied. 



The fact that the eggs in the ovaries of the females of the third column were often very 

 small indicates that the natatory bristles are probably broken off fairly soon after fertilization. 



With regard to the breaking off of the natatory bristles on the exopodite of the second 

 antenna it is. as G. W. MCller has pointed out, quite impossible that this is a case of accidental 

 mutilation. This is supported, not only by the reasons given by this author, but also by the 

 fact that the points of the bristles on the second to the fifth exopodite joint on this antenna are 

 practically never broken, although they are very fine and although these bristles are often 

 somewhat longer than the broken natatory bristles on the following joints. — With regard 

 to the way in which the long natatory bristles are broken off nothing can be decided with 

 certainty. It does not seem improbable to me, however, that G. W. MtiLLlili's assumption 

 that they are bitten off is correct. An investigation of these bristles on the females of the fourth 

 category gave a negative result; no structural alteration could be observed in the region where 

 the breaking off takes place. 



What happens to a female after her brood chamber has been emptied? 



It is perhaps too soon to give an opinion on this question. But it seems to me not 

 improbable that they die rather soon afterwards. This is indicated by the fact that no moults 

 seem to occur in the species of this genus after sexual maturity is attained. (Our knowledge 

 in this respect is, however, very limited; cf. G. W. MULLER, 1894, p. 188.) Without any moult 

 followed by a regeneration of the natatory bristles of the second antenna, it is, of course, imposs- 

 ible for these females to accompany^ the males when they soar aloft in the plankton. The 

 possibility of fertilization during a continued life in the mud of the bottom is, of course, not 

 excluded, but does not seem very probable. Nor is it impossible that a sufficient quantity of 

 sperm remains in the receptacida seminis for the fertilization of a new hatch of eggs. Nor, 

 of course, is the possibility of a parthenogenetic development of the eggs in the ovaries fully 



* At about the same time as G. W. Mijller a Swedish scientist Professor J. G. Andersson, who investigated the 

 Ostracod material of the Swedish Stale Museum, put forward quite the same hypotliesis; the results of his 

 investigations, wliich are still in manuscript, were, however, never published. I too arrived at the same result quite inde- 

 pendently of these two investigators. 



