BY H. L. kestbVkn. 65 



by their want of complete proof these suggested explanations 

 stimulate investigation and criticism, then even if they prove 

 wrong, they will have been productive of good. 



1. A. Conte (5), after experimenting with the free Nema- 

 tode, Rhabditis iiionokysteria, was enabled to record the fol- 

 lowing results : Grown on vegetable cultures, the worm was 

 viviparous, or occasionally the ova were extruded in well- 

 advanced stages of development, whereas grown in peptone, 

 the worm immediately becomes entirely oviparous, and many 

 of the eggs were in the two-blastomere stage. This extrusion 

 of the ova was not simply due to stimulation of the germina- 

 tive epithelium leading to distention of the oviduct and 

 uterus, for whilst viviparous females were observed carrying 

 over a hundred ova and a score of embryos, oviparoiis females 

 carried only six to eight eggs. An oviparous female placed 

 in vegetable culture rapidly became viviparous. 



2. Giard (10), P. Mayer (38), and Boas (2) have put on 

 record the fact that Palamoiietes varians, which lives at 

 times in the sea and at others in brackish water estuaries and 

 in branches of these which becoming cut off, are later con- 

 verted into fresh-water lakes, presents two varieties according 

 to its habitat. In one variety, the female, at the time of 

 gestation, contains 321 eggs 0-5 mm. in diameter (Mirroi/enifor 

 Giard), the other (Macroffenitor) at a like period 25 eggs 

 1-5 mm. in diameter; and, further, that the ontogeny of 

 the marine form, M irrof/enifor, is more extended than that of 

 the fresh-water form, in which the eggs contain a more abun- 

 dant nutritive yolk. Giard (9) states that a similar phenome- 

 non is to be observed among related Macrura, when one is a 

 fresh- water and the other a marine form. 



3. AJpheiis heterocheles, a Macruran, is, at Key West in 

 Florida, hatched in the form of the adult ; at the Bahama 

 Islands, the young go through five ecdyses before attaining 

 the adult form ; whilst, at Beaufort in Carolina, the larvae 

 are hatched in a stage intermediate between these two 

 (Herrick, 19). 



5 



