34 2 W. E. HOY, JR. 



author has actually counted the chromosomes in somatic cells or 

 has really meant the diploid number of chromosomes in the sex 

 cells. Since the two numbers are not alike in many animals, the 

 use of the former term in this connection should be abandoned. 



This is not intended to be an exhaustive list of the literature 

 on the subjects of spermatogenesis or oogenesis. Only where 

 accounts do not agree is reference made to more than one author. 

 A number of papers on oogenesis have reported counts of chromo- 

 somes in the early cleavage of the egg. For the most part these 

 reports have not been included here, since counts of the chromo- 

 somes in the first or second cleavages can hardly be considered 

 as conclusive of the somatic number, except where the Keimbahn 

 has been determined and where definite statement is made of the 

 particular cell in which the chromosomes were observed. When 

 the counts made in the early cleavage are followed up by counts 

 in the germ layers or their derivatives they then become of 

 significance. In this connection I have omitted the counts of 

 chromosomes in the early cleavage of Echinoderms, and of the 

 lower worms, in both of which groups numerous counts have 

 been made. Obviously, too, cases where only a few counts 

 have been made in one tissue are not at all conclusive when 

 unaccompanied by counts in other tissues. However, since these 

 are from definite somatic tissues they have been included here. 



In the alloiogenetic forms only the sexual generations are 

 included, since the purpose of this table is the comparison of the 

 number of the chromosomes in the sex cells with those in the 

 somatic cells. Investigation has been made on the chromosomes 

 of parthenogenetic individuals in a number of forms, particularly 

 in the Hymenoptera, the Aphididae, and in the Crustacea. 

 (Morgan, Stevens, etc.) 



Where two different numbers are given for the haploid or 

 reduced number, this refers to the fact that an accessory chromo- 

 some (or chromosomes) is present, and where the two haploid 

 numbers are the same, to the fact that idiochromosomes are 

 present, thus establishing a dimorphism of the spermatozoa in 

 both cases. Where different numbers separated by a hyphen 

 are given under either the diploid or haploid columns, a number 

 varying between the two has been found. 



