170 MONTGOMERY A STUDY OF THE CHROMOSOMES 



In the synapsis the twenty chromosomes unite to form ten bivalent ones, and the 

 two chromatin nucleoli to form one bivalent one. The latter is in later stages of the 

 growth period bilobed (N. 2, Fig. 86), is peripheral in position and not opposed to the 

 larger true nucleolus (N). 



In the monaster stage of the first maturation division are eleven chromatin segments 

 (Fig. 87), of which the smallest, centrally placed one is the chromatin nucleolus (N. 2) ; 

 all these elements are bivalent and on lateral view they all show the dumbbell-shape. 



17. Chariesterus anlennator Fabr. 



Two testes of this form were examined. 



In the rest stage of the spermatogonia I could not be certain of the presence of chro- 

 matin nucleoli, for my preparations were not very well stained to demonstrate them. 

 There were also no spermatogonic monasters favorable enough for determining the num- 

 ber of chromosomes. 



In the synapsis stage there is a bivalent chromatin nucleolus, but sometimes its com- 

 ponent parts are widely separated. 



In the telophase of the spermatocytes (PI. II, Fig. 88) the chromatin nucleolus (N. 

 #) is peripheral in position, sometimes its two univalent components still separated (but 

 that is not the case in Fig. 88). The true nucleolus (N) is sometimes central, sometimes 

 peripheral in position, and occasionally it is apposed to the chromatin nucleolus. 



In the monaster of the first maturation division (Fig. 89, lateral view ; Fig. 90, pole 

 view) are found thirteen chromatin segments, of which the smallest, centrally placed one 

 is the bivalent chromatin nucleolus (N. 2). Of the twelve chromosomes at least eleven 

 would seem to be bivalent (having the characteristic dumbbell-shape) ; but in the lateral 

 view here given (Fig. 89), it will be noted that the chromosome nearest the left-hand 

 side does not appear dumbbell-shaped. This may be a bivalent one seen obliquely, or it 

 may be a univalent one ; which is the case I cannot determine, since there were few 

 satisfactory lateral views on the preparations and since the number of chromosomes in 

 the spermatogouia could not be determined. 



18. Alydus pilosulus H. 8. 



Four testes of this species were studied. 



The chromatin nucleoli in the rest stage of the spermatogonia (N. 2, Fig. 91, PL 

 II) are two in number and rounded ; they are very small, usually close together, and 

 may be or not be attached to the true uucleolus (N). 



In the spermatogonic monaster stage (Fig. 92) are fourteen chromatin segments, l\v> 



