352 Transactions of the Society. 



asymmetrical and symmetrical type, the relation of the axes of 

 cleavage in the symmetrical type being inferred from the former. 



Numerical estimation of the bivalents is rendered difficult by 

 the disintegration of the plasmosome in diakinesis and the presence 

 of nucleolar fragments in metaphase sections, as indicated in 

 figs. 1(3-18. There was no sign of an accessory element in the 

 material at my disposal. 



The secondary spermatocyte division follows rapidly on the 

 first with intercalation of a short interphase ; such mitoses were 

 exceedingly rare in my material. The chromosomes show clumping 

 as Guyer and Cutler have recorded in Avian spermatogenesis ; 

 this may be an artefact due to defective technique. The recent 

 work of Hance and others on Diptera, as well as one or two 

 lateral views of anaphase in which the chromosomes seemed to be 

 well separated, would suggest that such is indeed the case. Con- 

 sequently the reduction divisions did not supply any critical data 

 for estimating the chromosome number of the species. The nature 

 of the reagent used for fixation excludes the possibility of adding 

 any significant observations respecting spermateleosis. 



The descriptive part of this research was carried out in the 

 laboratory of Prof. E. W. MacBride, F.K.S., to whom acknowledg- 

 ment is made by the author for time placed at his disposal for 

 original work. 



Eeferences. 



Cutler (1918). — Journ. Genetics, 7, p. 155. 

 Federley (1919). — Act. Soc. Scient. Fennicae, 48, No. 6. 

 Guyer (1916).— Biol. Bull., 31, p. 221. 

 Harvey (1920).— Journ. Morph., 34. 



HoGBEN (1920).— Proc. Roy. Soc, B. 91, p. 268; Ibid., p. 305. Linn 

 Soc. Journ,;, 35. Journ. Eoy. Microsc. Soc. (1920). 



(1921).— Proc. Roy. Soc, B. 92, p. 60. 



Jannsens (1900).— Anat. Anz., 17, p. 520. 



(1909).— La Cellule. 



Jordan (1914).— Science, 39, p. 438. 

 King (1913).— Anat. Record, 6, p. 405. 



LoYEZ (1905). — Arch, d'anatomie microscopique, 8, p. 69. 



Meves (1895).— Anat. Anz., 10, p. 365. 



ScHREiNBR. — Arch, de Biol. 



Seiler (1915).— Arch, fur Zellforsch., 13. 



Stevens (1912).— Biol. Bull., 22. 



Tellyesnicsky (1897). — Math. u. Naturwiss. Ber. Hungarn., 13, p. 303. 



Trinci (1908).— Mem. R. Accad, Sc Bologne. 



Winiwarter (1919). — Arch, de Biol., 30. 



