studios on marine Ostracods I'W 



somewhat fewer and less differentiated. The penis is small and simple and of an embryonal 

 appearance, resembling somewhat the simple type in the genus Philumedes. The f u r c a has 

 only nine claws, which in most cases decrease fairly uniformly in length the more proximally 

 they are situated. The lateral eyes, the median eye and the rod-shaped 

 organ are well developed. 



Female: This too is very like the mature stage. Shell: Average length, 2,1 mm.; 

 length: height = about 1,5: 1. All the limbs are well developed; the posterior ones are 

 of about the same type as in the male of this stage. The f u r c a has eleven claws — i. e. the 

 same number as in the mature stage — decreasing in most cases fairly uniforndy in length the 

 more proximally they are situated. The lateral eyes, the median eye and the 

 r o d - s h a p e d organ are well developed. The character by means of which this stage is 

 most easily distinguished from the mature stage — apart, of course, from the size — is the 

 larval appearance of the tissues. 



Stage II: — I was not successful in distinguishing with certainty between males and 

 females in this stage by means of dissection ; this may be due to the fact that the sexual characters 

 have not yet begun to develop or that all the specimens investigated were actually females. 

 Shell: Average length, 1,75 mm.; length: height = about 1,5:1. With regard to the 

 limbs it need only be mentioned here that they were all well developed, but they had, 

 especially the posterior ones, a still more larval appearance than in the preceding larval stage; 

 thus the cleaning limb — although it had proportionately about the same size as in the mature 

 stage — is armed with only about half the number of cleaning bristles. Each f u r c a 1 lamella 

 is armed with only nine claws, in most cases decreasing fairly uniformly in length the more 

 proximally they are situated. The lateral eyes, the median eye and the rod- 

 shaped organ are well developed. 



Stage III: — Shell: Average length, 1,4 mm.; length: height -- about 1,5:1. 

 All the limbs are developed in this larval stage too, but the cleaning limb is only 

 represented by an upward pointing appendage that is certainly rather long, but very slightly 

 differentiated; it has no cleaning bristles at all. The sixth limb, although of about 

 the definitive shape, is of a decidedly larval type; along the ventral margin of its end joint there 

 are, for instance, only six bristles, three anteriorly on the joint and three posteriorly; the former 

 are separated from the latter by a sharply marked gap. ( ) t h e i- 1 i m b s also have about 

 a definitive shape, while at the same time they present features that are even more larval than 

 in the preceding stage. Each f u r c a 1 lamella is furnished with eight claws, of which 

 the fourth is relatively short and weak, the others decreasing almost uniformly in length the 

 more proximally they are attached (note that only one specimen of this stage was investigated; 

 among larvae belonging to Stage I and Stage II single individuals were also observed with the 

 fourth furcal claw comparatively short and weak). The lateral eyes, the m e d i a n 

 eye and the rod -shaped organ are well developed; the median eye, however, 

 has rather weak pigmentation. 



Stage IV: — Shell: Average length, 1,2 mm.; length : height = about 1,5:1. 

 In this larval stage too all the limbs are present, the c 1 e a n i n g 1 i m b exists, however, only 



