432 



SCIENCE 



[N. S. Vol. XXVI. No. G66 



when kept for some houra in hyperalkaline 

 sea-water. They form a membrane and 

 throAV out the polar bodies. If we wait 

 until this occurs and then transfer the eggs 

 for from 2 to 3 hours at 15° C. into hyper- 

 tonic sea-water (50 c.c. sea-water plus 8 e.e. 

 2^n NaCl) and after this time bring the 

 eggs back into normal sea-water they de- 

 velop more quickly and more eggs segment 

 than if they remain permanently in the 

 hyperalkaline sea-water without any treat- 

 ment with hypertonic sea-water. 



Tlu-ee years ago I had found that a 

 small number of the eggs of moUusks, 

 Lottia gigantea, and various forms of 

 Acmcea, can be caused to develop if put 

 for 2 hours into hypertonic sea-water. I 

 have convinced myself this year that no 

 development occurs if they are treated with 

 a neutral hypertonic solution; that, how- 

 ever, if the alkalinity of the hypertonic 

 solution is raised sufficiently high by the 

 addition of NaHO many, if not practically 

 aU, the eggs of Lottia can be caused to de- 

 velop into larvEe. In these experiments it 

 was also noticed that the concentration of 

 the HO ions in the hypertonic solution 

 necessary for the production of larvas from 

 the unfertilized eggs differed considerably 

 for the eggs of different females. 



I have convinced myself also that the 

 unfertilized eggs of Sipimculus can be 

 caused to develop into larvas by putting 

 them permanently into a soliition with a 

 comparatively high concentration of HO 

 ions. 



As flar as the production of larvse from 

 unfertilized eggs with the aid of acids is 

 concerned, we may mention the eggs of 

 starfish, which can be cavised to develop 

 with the aid not only of the acids contain- 

 ing one carboxyl group, but apparently 

 with the aid of all acids. They differ in 

 this respect from the eggs of the sea-urchin. 

 It is possible that the acids with one eai'- 

 boxyl group act also better in the case of 



the starfish egg than the other acids; and 

 this might explain why Delage obtained 

 better results with COj than with other 

 acids, although according to my own ex- 

 perience the results with the other acids 

 are much more satisfactory than those of 

 Delage. 



For the eggs of the starfish the acid 

 treatment suffices, and no further treat- 

 ment with hypertonic sea-water is required. 

 In the egg of one form of starfish, namely, 

 Asterina., the spermatozoon causes a mem- 

 brane formation which is just as distinct 

 as in the sea-urchin egg. The membrane 

 formation can be induced in Asterina by 

 exactly the same methods as in the sea- 

 urchin egg, namely, a treatment with a fat 

 solvent (benzol, or amylen) or a fatty acid. 

 In these eggs the production of the mem- 

 brane is sufficient to cause the development 

 into normal larvte at least of a number of 

 eggs and an after-treatment with hypertonic 

 sea-water is not required. The starfish 

 eggs differ also from the sea-urchin eggs in 

 the former having a tendency to develop 

 spontaneously if left in sea-water, although 

 the number of eggs developing in this way 

 is, as a rule, very small. This development 

 may be due to the action of the HO ions 

 in the sea-water, or the action of an acid, 

 e. g., COo, formed in the egg itself. In 

 Asterina it can also be noticed that if eggs 

 remain in sea-water occasionally some of 

 them form a membrane spontaneously, 

 possibly also through the infiuenee of the 

 HO ions of the sea-water or an acid formed 

 in the egg. 



In the eggs of Tlialassema mellita, a 

 marine worm, Lefevre has produced mem- 

 brane formation and normal segmentation 

 by treating them with acid. The eggs of 

 this form are immature when removed 

 from the ovary, and the entrance of the 

 spermatozoon causes them to form a mem- 

 brane, to throw out their polar bodies, and 

 to segment and develop. Lefevre found 



