METHOD OF CELL DIVISION IN MONIEZIA. 



mands made upon it. . . . Further, if my interpretation of my ob- 

 servations be correct, then distinction between germ and somatic 

 plasm is obviously impossible; a special vehicle for the trans- 

 ference of heredity qualities is entirely wanting; such qualities 

 must be transmitted by the undifferentiated protoplasm; cell 

 lineage is manifestly lacking; a mosaic theory is plainly un- 

 tenable; and the fate of any given embryonic element whether 

 it shall form parenchyme, muscle, nerve, etc. must be deter- 

 mined by physiological causes alone." In an appendix referring 

 to Child's later papers Young says that he has verified Child's 

 conclusions upon the reproductive organs of TcEnia serrata. This, 

 of course, is exactly opposed to the work of v. Janicki and myself 

 upon T. serrata. I am not aware that he has published any 

 further account of these more recent observations. 1 



Balss ('08), in his extensive researches on the development 

 of the sex ducts of Anoplocephala and Solenophorns did not, I 

 believe, direct his attention to the method of nuclear division, 

 nor do his figures throw any light upon the question. His paper 

 is extremely valuable in making a study of the early stages of 

 sex organ formation. 



The last of the important papers on cestode histology is that 

 of Spatlich ('09) on Tetrabothrius. This author states that he 

 finds cases of amitosis and gives several figures of the cells in 

 question. He does not doubt that the cells are in the process o 

 amitotic division and certainly that is the easiest explanation 

 of the figures; but to one skeptically minded the proof will not 

 appear as conclusive. The cell in his Fig. 54, for example, might 

 easily be interpreted as a case of compression; while there is no 

 evidence that either of Figs. 54, 55 and 56 (drawn out nuclei, be- 

 coming dumb-bell shaped) would actually have completed the divi- 

 sion. Nothing is said of a complete series of stages. Further- 

 more, these are cases in the development of the " Dotterzelle " 

 and may perhaps have been at the end of their life cycle. 



In glancing over the list of tape-worms in which amitosis or 

 other irregularities of cell multiplication have been described, one 



'In Science of February 17, Young gives a very brief resume of this work. 

 Although he finds no mitosis, too few amitoses occur to account for the neces- 

 sary cell multiplication; he thinks that the "increase is partly due to development 

 of nuclei either de novo or from chromidial extrusions of preexistent nuclei." 



