Prof. K. Kossmaim on the Cryptoniscidce. 7 



certainly still more frequently missed by the observer. In 

 short I acce]}t it as proved that the female is copulated only in 

 the metamorphosed state. 



We have therefore free-swimming larviform males, and 

 adherent, strongly retrograded females, which copulate with 

 each other. But this is not all. My investigations furnish 

 the most convincing indications that the two forms are only 

 different stages of development of the same individual ; in 

 other words, that among the Cryptoniscidai we have to do 

 with di iJTotandrous hermaphrodism. According to the inves- 

 tigations of Bullar and Paul Mayer such a thing is not unpre- 

 cedented among Isopoda, but rather undoubtedly recognized 

 among Cymothoida^ ; there, however, the sexual maturity of 

 the male occurs much later, after the biramose natatory feet 

 upon the plcon, characteristic of the larva, have already 

 become transformed into branchial feet. Protandry with 

 larval sexual maturity was previously entirely unknown. 



Of course it has not been possible for me to trace one and 

 the same individual tlirough its whole course of development; 

 to observe how, as male, it performed the duties of its sex, 

 and how, after the metamorphosis had taken place, it was 

 copulated as a female, and produced eggs. I can therefore, 

 as already stated, only bring forward evidence in favour of 

 my assertions. 



First of all negative : — T have never found a free-swimming 

 Cryptoniscid larva of the last stage that had not male-deve- 

 loped sexual glands. I have found and examined of Grypto- 

 thir halani a considerable number, and of Eumetor three — all 

 males. Fraisse, indeed, describes female larvffi, but these 

 were already fixed, and not truly female, but immature, 

 neuter ; the free-swimming examples of which he found some, 

 were males. It is clear that the protandry is proved, unless 

 we succeed in discovering females or neuters in the same stage 

 of development as the males, hitherto exclusively found. 



A second piece of negative evidence is the following : — 

 While in all Bopyridaj s. str., and in the Entoniscidtc the 

 male becomes sedentary and remains with the female, it is in 

 all Cryptoniscidse free-swimming and exceedingly active, 

 and is often no longer to be met with near the fecundated 

 female. How should this difference between two so nearly 

 related groups be explicable if the male had not still another 

 task to fulfil elsewhere after the fecundation of the female ? and 

 what other can it be except that of itself growing into a female 

 upon another host ? 



Finally, we have a piece of positive evidence in the presence 

 in the mature female of a gland which is to be regarded almost 



