Vol. XXVIII. January, igi5. No. i 



BIOLOGICAL BULLETIN 



INITIATION OF DEVELOPMENT IN NEREIS. 



E. E. JUST. 



(From the Marine Biological Laboratory, Woods Hole, Mass., and the Physiological 

 Laboratory, Howard University School of Medicine, Washington, D. C.) 



If any apology be needed for merely adding to the long list of 

 eggs susceptible to agents of artificial parthenogenesis it may be 

 suggested that initiation of development in annelids possesses 

 some interest since annelid ova respond only with difificulty 

 to agents that induce development. ^ We need but recall the 

 case of ChcBtopterus (Loeb, 'oi5, Lillie '02, Allyn), oi Amphitrite 

 (Loeb, 'oia, Scott), of Po^ar^g (Treadwell), of the Pacific iVerm 

 (Loeb, '13), of Polynoe (Loeb, '07, '08) and of Nereis limhata 

 (Fischer, Lillie, '11, Loeb, '126, '13)2 to justify this statement. 

 In all these eggs differentiation without cleavage is far easier to 

 obtain than development closely simulating the normal. Among 

 diverse agents few only will give cleavage in Chcetopterus (Allyn, 

 Loeb and Wasteneys). The case of Thalassema stands almost 

 alone among annelids in giving development which is, according 

 to Lefevre, to a surprising degree like the normal. Another 

 instance among annelids of differentiation with cleavage arti- 

 ficially induced is worthy of note. 



This report, however, on the initiation of development in 

 Nereis by heat has, I think, special significance. The results 

 here offered require an interpretation which concerns the funda- 

 mental theory of parthenogenesis and fertilization. 



Experimental. 

 Certain preliminary experiments date from 1913. The ex- 

 periments given here were performed during June, July, and 



1 Bullot claims to have produced normal development in Ophelia with artificial 

 means. 



^Loeb's experiments with Nereis ('12) were apparently incomplete. ' 



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