ZOOLOGY AND BOTANY, MICROSCOPY, LTC. 179 1 



the last division, the chromatin in the nucleus of the primary spermato- 

 gonium becomes diffused, and a number of spiremes are formed, these 

 split and become short rods, the centrosomes appear, and two secondary 

 spermatogonia are thus produced. Round the two cells a membrane 

 appears, producing a two-cell spermatocyst. Each chromosome in the 

 new cells disintegrates, and at the same time reconstructs its share of 

 the nuclear membrane as a closed vessel round itself. Later these 

 vesicles become intercommunicating with one another, except for one — 

 that of the accessory chromosome — which remains apart in a separate 

 vesicle. The nuclear chromatin then passes through a spireme stage,, 

 splits, and breaks up as before to form chromosomes. The accessory 

 chromosome has no spireme stage, but splits up like the others. Divi- 

 sion then takes place, and this is repeated until each cyst contains 

 secondary spermatogonia of the seventh or eighth generation, when the 

 transformation into spermatocysts occurs. In the telophases of the last 

 ypermatogonial division the sacculations of the nucleus disappear, leav- 

 ing a smooth vesicular membrane to which the accessory chromosome 

 is applied. 



Prof. C. E. McClung* has studied the spermatocyte divisions in 

 Hippiscus plioenicopterus and other members of the iamily Acrididaa. 

 He finds that at the end of the last spermatogonial division, the daughter- 

 cells possess the somatic number of chromosomes. These break down 

 to form the spireme, except one which persists as the accessory chromo- 

 some. The thread splits longitudinally, and then at right angles to this 

 cleft, to form quadrivalent chromosomes. When separation takes place, 

 it occurs along the plane corresponding to the original longitudinal 

 cleft, without divergence of the constituent chromatids. Not till this 

 separation has taken place do the dyad chromatids begin to diverge from 

 one another, and form V-shaped structures. There is no rest-stage either 

 between spermatogonium and spermatocyte, or between first and second 

 spermatocyte division. In the last-named division there is a small 

 spindle, and the loosely joined chromatids separate easily at a point 

 which marks the previous cross-division. The author believes that this 

 sequence of longitudinal and cross-divisions is constant. The accessory 

 chromosome, after the appearance of the mitotic figure of the first sperma- 

 tocyte, takes its place with the other chromatic elements and divides. 

 Henceforth it becomes inconspicuous till the spermatids are formed, 

 when it again becomes distinct and conspicuous. In regard to its 

 function the author has no suggestion to make. 



Aquatic Insects in the Adirondacks. f— Prof. J. G. Needham and 

 Cornelius Betten publish a report based on ten weeks' work at the 

 Entomologic Field Station at Saranac Inn, New York, which illustrates 

 admirably the kind of work which can be done at such stations. The 

 primary object of the investigation was economic, in relation to the 

 food-supply of fishes, and the ten weeks' visit resulted in the working- 

 out of the life-histories of about 100 species of insects, the discovery of 

 ten new species and two new genera, and the accumulation of a large 

 amount of material still to be worked out. In the report the biological 



* Tom. cit., pp. 73-100 (3 pis.) 



t New York State Museum, Bulletin xlvii. (1901) pp. 383-012 (36 pis. and 

 42 figs.). 



N 2 



