1910.] NATURAL SCIENCES OF PHILADELPHIA. 311 



Automeris io. 



This species was found abundantly about Lansdowne, Pa., feeding 

 upon maple trees and rose bushes. The larvae pupated in September 

 and showed comparatively rapid development. The paired testes of Io 

 resemble those of other members of the Saturnids in position and color, 

 but differ in shape; instead of the kidney-shaped body, such as has 

 been described for C. promethea and /. polyphemus, each of the four 

 lobes of which it is composed is rounded and distinct, and the testes 

 become elongate by the two lateral lobes meeting in the centre and 

 the two distal ones being pushed longitudinally. As in the other 

 forms each testis has but a single vas deferens. 



Secondary spermatogonia are comparatively large cells with few 

 scattered chromatin granule- and a rather large plasmosome which 

 stains like chromatin and shows a loose structure (figs. 98 and 99), 

 and from which, as a center, short chromatin threads are seen to radiate, 

 suggesting the karyosphere described by Blackmail (1905 b) for 

 Scolopendra. Figs. 100, 101, and 102 show three stages in the last 

 spermatogonial divisions : controsomes are present with aster and spin- 

 dle fibres well developed, division is equal, and in telophase the massing 

 of the chromosomes is complete. The spermatogonial plates were 

 so condensed that all attempts to determine the number of the 

 chromosomes were unsuccessful. 



In going into the contraction stage the chromatin becomes looped 

 on the side of the nucleus, which lies toward the greater amount of 

 cytoplasm (figs. 103 and 104); then the loops begin to loosen, and in 

 early post-synapsis is seen for the first time a round darkly staining 

 body (fig. 106) which at this stage is quite small, but, as the skein 

 gradually loosens and the loops extend more and more into the nucleus, 

 this body, the idiochromosome, becomes more marked, and during 

 the growth period it is seen either as one or two round dark-staining 

 bodies. During this stage the centrosomes lie very near the inner 

 cell wall and from them flagellar grow out into the lumen of the cyst. 

 Fig. 109 shows a cell in the early rest stage; here the centrosomes are 

 single and the nagellum which grows from each is quite short. Fig. 

 110 shows a similar stage where the cell has grown to about twice the 

 size of that in fig. 109; in this, the centrosomes have divided and the 

 nagellum which grows from each centrosome is relatively long. 



In preparation for prophase it may be seen that the spireme has 

 broken into segments which are of various shapes and, in most cases, 

 so bent at the center as to suggest their formation by the union of 

 two chromosomes (fig. 111). These now split and join end to end to 



