102 N. M. Stevens 



however have been studied, Photinus pennsylvanicus and Pho- 

 tinus consanguineus. 



In Photinus consanguineus, all of the spermatocyte stages were 

 found in the testis of the adult in summer at Cold Spring Harbor, 

 and dividing spermatogonia were obtained from the larva in 

 October. In the adults of Photinus pennsylvanicus only ripe 

 spermatozoa were present; in the larvae collected in October and 

 November, only spermatogonia and growth stages of the sperma- 

 tocytes. A large number of larvae were collected and kept during 

 the winter in battery jars with a piece of turf in the bottom. 

 Some of the jars were placed in the greenhouse, others in a cool 

 basement room. The material from both sets of jars was tested 

 from time to time with aceto-carmine, but not until May w^hen 

 the larvae were beginning to pupate, were any maturation mitoses 

 found. From May 8 to May 13 both larvae and pupae furnished 

 good material. As in Tenebrio molitor, the pupae contained favor- 

 able divisions in somatic cells. 



Fig. 2 is the equatorial plate of an oogonium of Photinus 

 pennsylvanicus, from an ovary sectioned in October. There 

 are twenty chromosomes, two longer and two shorter than the 

 others. The two smallest correspond to the small odd chromo- 

 some {x) of the male, seen in Fig. 3, the spermatogonial plate 

 of nineteen chromosomes. Fig. 4 is an equatorial plate from a 

 male somatic cell, found in mitosis in the digestive tract of a 

 male pupa. In Ellychnia corrusca the synizesis and synapsis 

 stages are similar to those previously described for several of the 

 Coleoptera (Stevens '06, PI. IX, Figs. 37 to 42, 61 to 62, and PI. 

 XII, 153 to i54;Nowlin'o6, PI. I, Figs. 2to5, and PI. II, Figs. 52 

 to 54) — a dense group of short loops at one end of the nucleus in 

 synizesis, followed by a stage in which the loops straighten and 

 unite in pairs. In Photinus pennsylvanicus these stages are quite 

 different. After the last spermatogonial division, the chromo- 

 somes evidently remain condensed for some time, for we find many 

 cysts on the border line between spermatogonia and spermato- 

 cytes in which the nuclei have the appearance of Fig. 5. A slightly 

 later stage shows the chromosomes more crowded together and 

 at one side of the nuclear space. The next stage, which might 



