62 H. B. GOODRICH 



opposed by but a single Y. The earlier work on this material, 

 so satisfactory for a study of the maturation divisions, gave 

 promise that it might likewise be favorable for a detailed study 

 of the earlier stages with especial reference to synapsis and 

 to the history of the X-chromatin. In this respect expectations 

 have not been fully realized. The force of Gregoire's reference 

 to Ascaris megalocephala as "Get object difficile," is most 

 clear; but nevertheless Ascaris incurva has, for these stages, 

 proved more favorable than the better known form. The re- 

 sults show that the history of the events preceding the matura- 

 tion of the germ cells in Ascaris, while differing in details from 

 that of other forms, is not exceptional among animals in regard 

 to the interpretation of the process of reduction. Here are 

 also presented observations on dimorphism of the spermatozoa, 

 on the early cleavage stages and on the spindle formations in 

 the heterotypic mitosis as well as on the growth stages. The 

 results set forth in the preliminary report were embodied in 

 the following formulae presenting the cycle of the chromosomes. 

 Autosomes are designated as A and the sex-chromosomes as 

 X and Y. 



Spermatozoa Egg Zygote 



13A + 8X + 13A + 8X = 26A + 16X = 42 (female 



13A + Y + ISA + 8X = 26A + 8X+Y = 35 (male) 



MATERIAL AND TECHNIQUE 



Ascaris incurva, Rud. is parasitic in the stomach of the ^^ord- 

 fish, Xiphias gladius Linn. The material was obtained dur- 

 ing the summers 1913, '14 and '15 at Woods Hole. These 

 parasites have been found in every sword-fish examined, but 

 unfortunatelj^ the occurrence of the host in that locality is sub- 

 ject to a marked yearly variation. The animals were dissected 

 in physiological salt solutions or in the body fluid only; the gonads 

 were uncoiled and at once transferred to the fixing fluid. Many 

 fixatives were used; those most successful have been: Hermann's 

 fluid which is excellent for all stages but adapted alone for a 

 study of the spindle fibers; strong Flemming's fluid; the modified 



