160 EZRA ALLEN 



Neither he nor Duesberg touch upon fiber attachment. This 

 aspect of mitosis is discussed by McClung ('14), who finds that 

 for most of the Acrididae terminal attachment is characteristic. 

 In four genera, however (Stenobothrus, Chorthippus, Chloealtis, 

 and Trimerotropis) , certain chromosomes in the complex have 

 intermediate fiber attachment. The correspondence in fiber 

 attachment between the rat and the Acrididae in general is of 

 much interest because no other instances have been recorded 

 where this mode of attachment is constant in the complex. It 

 will be of interest to learn if it is characteristic of rodents or 

 peculiar to the rat. There is at present no comparative data 

 for any of the mammalia on this point. This persistence of 

 fiber attachment throughout the history of the chromosomes is 

 also another illustration of the close relationship between the 

 tetrad and archoplasmic organization (McClung, '16, p. 675). 



The spermatogonia and Sertoli cells 



The chief questions of interest here center about the origin 

 and relationships of the spermatogonia and the Sertoli cells, 

 and whether there is more than one kind of spermatogonium. 

 Of associated importance are the number of spermatogonia! 

 divisions and the mode of chromosome division. 



The first of these problems arises from the presence in the adult 

 tissue of three kinds of cells along the basement membrane. 

 These have been variously interpreted. One kind, the Sertoli 

 cell, was early distinguished and its function interpreted, but its 

 origin is still in dispute. The other two kinds of cell have had at 

 least three distinct interpretations. They are the ones which 

 I have described as type A and type B. Type A was regarded by 

 some as a mother cell of both type B and the Sertoli cells. As 

 such it has received various names, such as spore cell (Brown, 

 '85), Stammmutterzelle (Benda, '87), gonie poussiereux (Regaud, 

 '00), and indifferent cell (Schoenfeld, '01). 



Regaud's interpretation ('00) of the origin of this indifferent 

 cell in the rat was that it was produced by the amitotic division 

 of the nuclei of the Sertoli cells, which he thought formed a 



