THE JOURNAL 



OF 



THE LINNEAN SOCIETY, 



(ZOOLOGY.) 



The Spermatogenesis of Stenohothrus inridulns ; witli Special Reference to 

 the Heterotropic Chromosome as a tSex Determinant in Grasshoppers. 

 By Capt. C. F. U. Meek, F.L.S. 



(Plates 1-3.) 



[Read 1st December, 1910.] 



Inteoduction. 



Since Van Beneden discovered in 1883 that the somatic number o£ chromo- 

 somes is halved in the mature germ-cells of both sexes, the attention of 

 investigators has been turned to the phenomena of the maturation divisions 

 and to the problems to which they give rise. The literature upon spermato- 

 genesis and oogenesis has become very extensive^ and it is impossible to 

 discuss here the numerous questions that have arisen during the last few 

 years. I shall therefore touch only upon certain points of controversy, 

 directly concerned with the morphology and function of the chromosomes. 



Although the halving of the somatic number of chromosomes is no longer 

 denied, considerable disagreement exists as to the manner in which reduction 

 is effected. In the eumitotic type of maturation^ both mitoses are regarded 

 as being equational; but the majority of cytologists uphold the doctrine of 

 pseudomitosis, in which one maturation division is reductional. They have, 

 however, not decided whether this division is the first or second ; and in this 

 way the rival theories of Pre-reduction and Post-reduction have arisen. 



The researches of vom Rath in 1892-5 upon the spermatogenesis of 



LINN. JOURN. — ZOOLOGY, VOL. XXXII. 1 



