190 



MONTGOMERY — A STUDY OF THE CHROMOSOMES 



PHYMATII) .K. 



32. Phi/mala sp. (P. wolffii Stal. ?). 



Nine testes of this species were studied. 



In the rest stage of the spermatogonium there are two chromatin nucleoli (iV. 2, 

 Fig. 199, PL V), usually unequal in size ; frequently one or both of them is in contact 

 with the true nucleolus (N). 



In the spermatogone monaster are seen on pole view (Fig. 200) thirty chromatin 

 elements; two of these certainly represent the chromatin nucleoli, but they offer no pecu- 

 liarities by which they can be distinguished from the twenty-eight small chromosomes. 



In the synapsis stage the twenty-eight chromosomes unite to form fourteen bivalent 

 ones, and the two chromatin nucleoli to form one bivalent one. The latter is in the telo- 

 phase and rest stage of the spermatocyte (Fig. 201) clearly transversely constricted, show- 

 ing its bipartite nature, and is always apposed to the surface of the larger true nucleolus 

 (Fig. 201, K). 



Pole views of the monaster stage of the first maturation division (Fig. 202) always 

 show exactly fifteen chromatin elements, namely, fourteen chromosomes and one chroma- 

 tin nucleolus. All these elements are found to be dumbbell-shaped on lateral view (Fig. 

 203, showing eight of them), so that all are bivalent. The chromatin nucleolus cannot be 

 distinguished in size from the chromosomes. 



N All I O.K. 



33. Coriscus ferns Linn. 



Three testes of this species were studied. 



The relations of the chromatin nucleoli were not determined in the small nuclei of 

 the spermatogonia, and the spermatogonia mitoses were not favorable for counting the 

 small, rounded chromosomes. 



In the growth period of the spermatocytes there is usually one large bivalent 

 chromatin nucleolus, with its component parts in close apposition (N. 2, Fig. 20f>, PI. V), 

 attached to the true nucleolus (IV). Sometimes its component parts (which are of equal 

 volume) are separated from one another, and then both may be attached to the same true 

 nucleolus (Fig. 204), or fchey may be apposed to separate nucleoli, or only one of them 

 may be apposed to a nucleolus (of which there are generally two, sometimes three). Be- 

 sides the large, bivalent chromatin nucleolus can be seen in most nuclei a much smaller 

 chromatin nucleolus (Fig. 205) which stains like the larger one; it is generally close to 

 the nuclear membrane, but is occasionally apposed to a true nucleolus. 



In the first maturation division there are ten chromatin elements (Fig. 200, in which 



