220 



tary appearance, in the present form it was well developed, even extending con- 

 siderably beyond the outer. One of the two specimens (fig. 2 b) was found, 

 on a closer examination, to be just about to cast off its skin, and within the 

 pellucid envelope a quite normal Cryptoniscian larva could be discerned, exactly 

 agreeing with a form that I had previously not infrequently found free in the sea 

 (fig. 2 c). The latter exhibits all the characters indicated by Dr. Hansen 1 ) as 

 peculiar to the larvae belonging to the family Cryptoniscidce, and some of these 

 characters could also be very distinctly seen in the Microniscus stage mentioned 

 above (cf. the detail figures 2 b and 2 c). 



From the two above given series of observations, it is thus clearly shown, 

 firstly, that a true Microniscus, apparently identical with the form previously 

 recorded by the present author as M. calani, develops from the 1st stage 

 of a normal Bopyrid lai'va; secondly, that another form of Microniscus, after 

 having attained its normal development, is transformed by a single exuviation into 

 the well-known 2nd larval stage, generally termed the Cryptoniscian stage ; thirdly, 

 that these 2 forms of Microniscus, though exhibiting a very similar appearance, 

 in reality belong to 2 very different families of Epicarida, the one to the Bopij- 

 ridce, the other to the Cryptoniscidce. In other words the name Microniscus 

 cannot in future be taken in the formerly-adopted sense as a generic denomi- 

 nation, but must be restricted to designate a transitory developmental stage of 

 Epicarida connecting the 2 previously-known larval stages. 



It is rather difficult at present to state with certainty, to which species 

 of Epicarida the 2 above-mentioned Micronisci belong ; but I am much inclined 

 to believe that the one form will turn out to be a developing stage of Phryxus 

 abdominalisj and the other a similar stage of a species belonging to the genus 

 Podascon of Gdard and Bonnier. 



Isopoda, Cumacea and Stomatopoda of the German Plankton-Expedition, p. 22.' 



