AUOUST24, 1900.] 



SCIENCE. 



307 



hand it is similar to C. irroratus in the 

 shape of the nine teeth on the antero-lateral 

 margin of the carapace, and in the straight 

 postero-lateral margin of the same. It is 

 rounder, narrower, the carapace more con- 

 vex, and the body in general more hairy 

 than either of the existing species. 



It thus seems most probable that the 

 miocene species, being a more generalized, 

 composite form, is the ancestor from which, 

 either toward the end of the pliocene or 

 the beginning of the quaternary period, the 

 two living species sprang. C. irroratus has 

 inherited the exact shape of the lateral 

 teeth and the shape of the postero-lateral 

 margin of C. proavitus, while C. horealis has 

 retained the higher spine-like granulations 

 or submuricate feature of the carapace and 

 hand and the hairiness of the body. 



On the whole the evidence that our two 

 northeastern species have descended from 

 a much more rounded, convex, and hairy 

 miocene form living in the same geograph- 

 ical area seems to be well established. 



It would be most interesting to compare 

 this fossil species with very young individ- 

 uals of our living species, but after inquiry 

 I find that they are not in existence in our 

 museums. It is to be hoped that speci- 

 mens of the very young may be collected 

 and compared with the fossil species. It 

 is known that in cancer the body grows 

 wider with age. 



A Review of the Problem of Sex Cells in the 



Hydromedusce : By Chaeleb W. Haegitt, 



Syracuse University. 



A former paper before this section (Proc. 



A. A. A. S., 1889) set forth the view that 



for Eudendrium ramosum the ova originate 



in the endoderm. This was not passed 



without controversy. As a preliminary 



contribution it was not emphasized at that 



time. After some years the problem was 



again taken up in connection with related 



problems and four species of Eudendrida 



examined, namely, E. ramosum, E. raeemo- 

 sum, E. dispar, and E. tenue. 



As a result it may be said that while in 

 E. ramosum and E. tenue the ova arise 

 strictly in the endoderm, and never at any 

 time find their way into the ectoderm, in 

 the species racemosum and dispar these prod- 

 ucts are found abundantly in both tissues. 

 However, it must not be overlooked that in 

 every case the primitive ova are found in 

 the endoderm, and only during the process 

 of growth do they migrate into the ecto- 

 derm. In view of these facts it would seem 

 to be a just inference that their origin is 

 endodermal, though in these two species 

 they may migrate into the ectoderm and 

 complete development in that position. 



Any glance at the literature will show a 

 a strange confusion as to data. Weismann 

 himself has contributed to this, due in part 

 to confusion arising in methods of work, 

 done in part upon optical sections rather 

 than actual. Similar errors have doubtless 

 been due to similar methods by earlier as 

 well as later observers. 



However, it seems that in Hydromedusse 

 there is a great variation in this matter. 

 For whether the hydroid or medusa be the 

 more primitive, or likewise as to the more 

 primitive character of hydro- or scypho- 

 medusa, there must have been a time when 

 there was a transition from the one to the 

 other. If therefore such transitions have 

 arisen phylogenetically, is it not possible 

 that among the more plastic genera such 

 transition may continue at the present time ? 



In any case it would seem to be extremely 

 rash to predicate any such character as a 

 diagnostic and distinctive difference be- 

 tween the sub-classes Hydromedusse and 

 Scyhhomedusse. 



The Mosaic of the Single and Twin Cones in 

 the Retina of Micropterus salmoides : By 

 George D. Shafee, Indiana University. 

 In the American Naturalist for February, 



