INDIVIDUALITY OF CHROMOSOMES. / 



There is here one frequently showing an L shape somewhat as 

 Sinety (28) has described in a Phasmid, but this is not the acces- 

 sory joined to an ordinary chromosome as Sinety interpreted his 

 figure. 



In G. domcsticus in the spermatogonia there are twenty ordi- 

 nary chromosomes as shown in Figs, i and 2. These show 

 differences of size and also in amount of curving. The short 

 ones are straight or almost so, and the long ones are curved, 

 some more, some less. The amount of curving does not depend 

 on the length only as can be seen by comparing chromosome 

 pairs 5 and 6 in Fig. 2. The chromosomes can be arranged 

 into a graded series of pairs following Sutton (30) and Mont- 

 gomery (25) but the differences between certain pairs is often very 

 slight so that one could often as well make groups of three's or 

 four's. In Fig. 2 I have made an attempt to bring together 

 the probable pairs, but in many cases the arrangement is very 

 unsatisfactory. Of course, looking at the chromosomes them- 

 selves with adjusting focus relations are more apparent than can 

 be indicated by a camera drawing. In pairs one and two of Fig. 

 2 the two chromosomes on the right side of the respective pairs 

 may belong together to form one pair, and the two on the left 

 the other. Grouping them as suggested would bring together 

 chromosomes that do not differ more than do some of the chro- 

 mosomes of the pairs as they now stand, e. g., pair 3. 



After the spermatogonial divisions are completed the cells 

 enter the growth period. The chromosomes seem at first to 

 break up and the chromatin apparently becomes diffuse, yet it 

 appears partly in threads as shown in Fig. 4. I have looked very 

 long and carefully for a massing of the chromatin thread into one 

 part of the nucleus hoping thus to find what Montgomery (22) 

 had described as the " synapsis stage " I was unable to find any- 

 thing that corresponded with his description or drawings, although 

 he named Gryllus as one of the forms in which he saw the syn- 

 apsis stage. But upon studying the ovocytes during the growth 

 period I found many cells showing the conditions indicated in 

 Fig. 36. This drawing is made from an ovary taken from Scap- 

 leriscus didactylns, a Porto Rican mole cricket, kindly sent me by 

 O. W. Barrett, of the agricultural experiment station. Both 



