190 A. C. WALTON 



and the results seem to show definitely the presence of an X-type 

 idiosome attached to the end of an autosome. 



iSIATERIALS AND METHODS 



The material used was obtained from freshly killed cats. The 

 worms were immediately removed from the intestine of the 

 host, placed in normal salt solution and kept at body tempera- 

 ture until they could be killed. The posterior end of the worm 

 was clipped off and the testes were at once stripped out on the 

 glass plate and fixed. Hermann's fluid and Flemming's fluid 

 (strong) were found to give the most satisfactory fixations. The 

 sections of the testes were made 4 m to 8 ^ in thickness. In gen- 

 eral the material was stained by a modified iron-alum-haema- 

 toxylin method; dilute Delafield's haematoxylin being used 

 after the mordant in the place of ^ per cent aqueous solution of 

 haematoxylin. This method, as in earlier work (Walton, '16 a), 

 gives a better contrast between the chromatin matter and the 

 yolk granules than can be obtained by the usual iron-alum- 

 haematoxylin method of Heidenhain. Orange G and Bordeaux 

 red were used as counter-stains. 



EXPERIMENTAL EVIDENCE 



a. Spermatogonia 



As is the case in A. canis, the spermatogonia of A. felis 

 are very small and the nuclear material tends to clump to such 

 a degree that but little evidence can be gained by their study as 

 to the chromosomal number. The spindle and centrosomes are 

 quite distinct, however. This 'mass' division was closely 

 studied. Of 430 cells examined during spermatogonial meta- 

 phases, 271 of these showed the presence of both a large and a 

 small clump of chromatin material passing to each pole of the 

 mitotic figure. The smaller clump of chromatin was apparently 

 one-tenth of the size of the larger mass. The smaller clump of 

 chromatin varied considerably in position ; sometimes lying close 

 to the larger body, and even connected to it by chromatin 

 strands, and again, lagging far behind, widely separated from the 

 main mass as it progressed towards the poles of the spindle. 



