Artificial Parthenogenesis in Thalassema MelUta 99 



and experiments with salts were discontinued. It is not im- 

 possible that favorable solutions of these and other salts might 

 have been found which w^ould have caused development, had the 

 attempt been made to investigate the action of salts in greater 

 detail. 



I was also unable to obtain parthenogenetic development by 

 mechanical agitation or by exposure of the eggs to low tempera- 

 tures. Unlike Asterias and Amphitrite, the eggs of Thalassema show 

 no changes whatever after either gentle or violent agitation, and 

 the low temperatures which Greeley ('02) found to be capable of 

 producing development of the unfertilized eggs of the starfish were 

 utterly ineffectual in bringing about a similar result in the case 

 of Thalassema. On the other hand, parthenogenetic develop- 

 ment, which was strikingly normal in a great many experiments, 

 took place after treatment of the eggs for several minutes with 

 dilute solutions of certain ^.cids. Nitric, hydrochloric, sulphuric, 

 carbonic, acetic and oxalic acids were employed, and all yielded 

 about equally successful results. 



I Acids as Parthenogenetic Agents 



The method of causing artificial parthenogenesis by the use of 

 mineral acids was first elaborated by Loeb and Neilsori ('01), who 



employed a solution of 3-5 cc. — inorganic acid + 100 cc. sea-water, 



with an immersion of 3-20 minutes, and in the case of Asterias 

 succeeded by this means in bringing about 20 per cent of the eggs 

 to a gastrula stage. They ascribed the result to the specific action 

 of H-ions. Since these initial experiments, inorganic acids have 

 been used with some success as parthenogenetic agents by Loeb 

 and others on the eggs of echinoderms and worms. 



The use of CO2 in artificial parthenogenesis is due to Delage 

 ('02, '04) who found the method to be remarkably successful with 

 the eggs of the starfish. The eggs were placed in sea-water charged 

 with CO2 by means of a "sparklet," and after an immersion in 

 the charged sea-water for about an hour, practically every egg 

 developed into a swimming larva. The larvae were kept alive for 

 three and one-half months, and were reared to the beginning of 



