The determination of sex in animal development. 739 



Aerzte", Jahrg. 10, No. 1, 1901, p. 1 — 11, also under the same title 

 and with 8 figures in Verh. anat. Ges., 1901, Bonn, p. 23 — 36). 



Holmgren's record of two kinds of spermatozoa in one of the 

 Coleoptera suggests the inquiry whether the second form of sperm may 

 not in fact sometimes or often be functional as well as the usual 

 sperm. The order of Coleopterous insects is very large, embracing 

 more than 70 000 species. The Insecta form an immense group, 

 not fewer than 250 000 species being known. Probably in a thousand 

 years the spermatogenesis of not a tithe of either the Insecta, or of 

 its order of Coleoptera, will have been worked out! This reflection 

 bears significantly upon the question of the relativity of human 

 knowledge. Naturally, we cannot wait another thousand years before 

 drawing our conclusions: we can only say, that in our experience a 

 second form is never functional, and that, though it be very often 

 diflerentiated, there is no great likelihood of its ever being found to 

 be of functional value alongside the usual form of sperm, and in 

 addition to this. 



The exceedingly interesting and important recent work of Meves, 

 referred to above, affords additional evidence of the probable truth 

 of this. Meves has studied the spermatogenesis of Paludina in much 

 greater detail than any preceding observer. He records, that in the 

 spermatogenesis of Paludina there is no reduction of chromosomes in 

 the spermatogonia of the worm-hke sperm. A most curious irregular 

 reduction takes place in the first of the two ensuing divisions, for 

 details of which the reader may be referred to the original, and the 

 final result is, that each spermatid, resulting from the second mitosis, 

 contains but one chromosome. The normal number of chromosomes 

 in Paludina is, according to Meves, 14, the reduced number 7. Here, 

 therefore, instead of 7 chromosomes each spermatozoon contains but 

 the equivalent of one. In Pygaera, according to the same observer, 

 in the formation of the non -functional form of spermatozoon chromatic 

 material, in other words chromosomes, find no place, "in Pygaera the 

 second form of spermatozoon is completely destitute of nuclear portion, 

 that is, it is headless" (Meves). Notwithstanding Meves' cautiously 

 expressed opinions to the contrary, there would appear to be no 

 escape from the conclusion, that, even the complete differentiation of 

 the second form of sperm in Paludina and Pygaera being accompanied 

 by phenomena, only diagnostic as degenerative, it can be of no func- 

 tional import whatsoever. 



