547 



three species ^), Moniezia expansa, M. planissima, and M. trigonophora 

 have been examined, all are essentially similar as regards cytological 

 features. 



This account of the technique employed has been given in some 

 detail because I desire to leave no opening for possible objections on 

 the ground of imperfect technique or insufficient data. 



The results obtained with the new material only confirm my earlier 

 observations. During the formation and growth of the proglottid the 

 increase in the number of nuclei is enormous and almost the whole 

 of this increase is the result of amitotic division. In the present paper 

 I desire to call attention chiefly to the occurrence of amitosis as a 

 characteristic feature in the development of the reproductive organs : 

 other observations are reserved for a later account. 



In an earlier paper-) in which the formation and growth of the 

 proglottids was described it was noted that the reproductive organs 

 develop from the parenchymal syncytium. My observations indicate 

 that there is little migration of cells or nuclei but rather a develop- 

 ment of each part in situ. The earliest stages in the formation of 

 the reproductive organs consist in a multiplication of the parenchymal 

 nuclei of particular regions. As development goes on the stimulus 

 which determines this multiplication affects a larger and larger area, 

 as in the case^of the female organs, or new areas, as in the case of 

 the testes, and each part of the area or areas thus affected develops 

 into that portion of the reproductive organs which is characteristic 

 of this region. So far as my observations go, and they cover several 

 thousand sections, no case of mitosis has ever been observed in the 

 earlier stages of the development of the reproductive organs. 



Description of Amitosis. 



Before taking up the development of the reproductive organs a 

 brief account of the nuclei and the characteristic features of their 

 amitotic division must be given. 



All the nuclei in the body of Moniezia except those of the sexual 

 cells in later stages of development are very similar in appearance 

 though great difference in size occurs. In general, each nucleus possesses 

 a single large, deeply staining nucleolus. In cases where the extraction 



1) Stiles and Hassall, A Revision of the Adult Gastodes of Cattle, 

 Sheep, and Allied Animals. Bull. 4. Bureau of Animal Industry, U. S. 

 Department of Agriculture, 1893. 



2) Abnormalities in the Cestode Moniezia expansa, III. Biol. Bull., 

 Vol. 3., Nos. 3 and 4, 1902. 



35* 



