669 



the recurved tips of the chelae; the simple telson; the ratio of the length 

 of the larva to the diameter of the egg, which is about two to one for 

 the first and three to one for the second stage; the nakedness of the ear 

 pit and the small number of the segments in the second antenna. 



The chief resemblances to the second stage are : the greater deve- 

 lopment of the first antenna in having five segments in the exopodite 

 in place of four and in having five sense hairs while in the first stage the 

 other Cambari have none and the Astacus but one, though in the second 

 stage the four crayfish above mentioned have 5. 5. 7. 8., in the order 

 above given; the dentation of the mandibles, which, however in a se- 

 cond stage should have six or seven, in place of three or four teeth; the 

 size and straigtness of the rostrum; the great perfection of the last pair 

 of pleopods. 



In brief the larvae found on these Mexican crayfish would be re- 

 garded as of the first stage from the chelae and external appearance of 

 the telson, but as in the second stage from the first antennae and the 

 advanced condition of the last pleopods inside the telson. 



Having shown that the recurved chelae and the simplicity of the 

 telson are intimately connected in other crayfish, in all as far as known, 

 with the peculiar dependence of the first stage upon the mother, and 

 not knowing the value of the development of the sense clubs as distin- 

 guishing first and second stages, we will conclude that these larvae are 

 in the first stage. 



However as first stage larvae they differ from other species known, 

 in the perfection of sensory clubs, size of spinules, dentation of mandi- 

 bles, and the perfection of the last pleopods. 



In these respects they support the view, elsewhere maintained, that 

 the early larvae of Cambari have degenerated from more active forms 

 in connection with a life of dependence upon the mother for in the 

 Mexican region where Cambari are supposed to have departed from 

 Astacus-\\ke. ancestors we might expect to find more of an orginal larval 

 life remaining and, at all events, less of the more extreme adjustment 

 which the most specialized northern larvae have developed in their more 

 complete parasitism upon the mother. 



Baltimore, December 9. 



2. Limnocodium im Jantsekiang, 



eine neue Süßwassermeduse aus China. 

 Von Dr. Asajiro Oka, Tokio. 



eingeg. 23. Dezember 1907. 

 Vor einiger Zeit erhielt ich aus China unter anderm zehn Exem- 

 plare einer Süßwassermeduse, die von Herrn M. Kawai, Kapitän eines 



