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doubt that amitosis plays an important part in growth and regulation 

 in Planaria. 



Bipaliumkewense. In a number of specimens of this tropical 

 triclad, which can often be obtained from conservatories, examination 

 of the sections of pieces during regulation showed frequent cases of 

 apparent amitosis and almost no mitosis. The forms of division are 

 similar to those in Planaria. 



L e p t o p 1 a n a t r e m e 11 a r i s. In the regenerating tissues nuclear 

 phenomena similar to those in Planaria are of frequent occurrence and 

 mitosis is very rare. 



Trematod a. 

 Pneumonoeces medioplexus. Having observed a surprising 

 infrequency of mitosis in the primitive germ cells of the testis of this 

 species, I suggested further work along this line to Mr. C. F. Adams 

 who found in this region numerous cases which could not be inter- 

 preted as any thing else than amitosis. The results of his work will 

 appear elsewhere. I have also found frequent amitosis in the paren- 

 chyma of these and other trematodes. 



C e s t o d a. 



Moniezia expansa; Moniezia planissima. A brief 

 account of my observations on these forms has already appeared 

 (Child, '04) and a more extended paper is in press. Here mitoses are 

 very rare in the earlier stages of development of the testes and ovaries, 

 while undoubted amitoses are frequent. Outside the reproductive 

 organs mitosis is almost never seen in any region even in the "neck- 

 region" where the nuclei are multiplying with great rapidty. Al- 

 though the nuclei are small, undoubted amitoses can readily be observed 

 with proper preparation. In the cleavage of the egg the first division 

 is probably always mitotic and often some of the following cleavages, 

 but amitosis soon replaces mitosis in the smaller cells, though the 

 larger, which divide more slowly, may show mitosis in later stages. 



The apparent absence of mitosis in cestodes has been noted by 

 various authors. Even as late as 1905 Spengel ('05) in the course 

 of discussion at the meeting of the Deutsche Zoologische Gesellschaft 

 called attention to this peculiarity: "Ferner weist er (Spengel) auf 

 die allen entwickelungsgeschichtlichen Untersuchungen an Trematoden 

 und Cestoden sehr hindernd im Wege stehende Tatsache hin, daß es 

 nicht gelingt, mitotische oder amitotische Zellteilungen dabei zu be- 

 obachten." Evidently Spengel was not aware that I had already 

 observed amitosis in cestodes (Child, '04). 



