Jan., 1906.] Occurrence of Sex in Organs in Aelosoma. 
437 
the nuclei lie at the outer ends of their cells; each contains a 
closely packed ball of chromatin granules, separated from the 
nuclear membrane by a slight space, while at the periphery of the 
nucleus is a large and conspicuous nucleolus (plasmasome) . The 
cytoplasm is faintly granular. The secondary spermatocytes 
make up cell masses similar to those of the primary spermato- 
cytes, differing from the latter only in the size and number of 
the component cells. The cell masses of which the spermatids are 
composed, however, present a very different appearance, (Fig. 
4). The nuclei, although now much reduced in size, still show 
the closely packed ball of chromatin granules and the prominent 
nucleolus characteristic of the two former stages, and have also 
Fig. 1. Portion of a cross-section through seventh segment, two ova 
(ov.), lying between the stomach wall (st.), and the ventral hypodermis 
(hyp.); Fig. 2, primary spermatocytes; Fig. . ‘3, secondary spermatocvtes; 
Fig. 4, spermatids; Fig. .5, spermatozoa. Fig. I,x77(); Figs. 2-.5. x K).5(). 
maintained their position at the periphery of the cell mass. Each 
nucleus is now surrounded by an area of clear cytoplasm, the 
clear areas of the different cells being contigous, so that the cell 
mass is divided into an external zone of clear and transparent 
cytoplasm, within which is a mass of darkly granular cytoplasm, 
which already shows signs of vacuolization. This latter mass, 
of course, represents the inner ends of the spermatids. Between 
the spermatids and the ripe spermatozoa, no intermediate stages 
were found. The spermatozoa, (Fig. 5), consist of a long fusi- 
form chromatic portion, which no doubt represents the sperm- 
atid nucleus, and which tapers posteriorly to join with a slender 
tail, composed of clear cytoplasm. The anterior end of the 
chromatic portion is sharply truncate, and somewhat concave. 
In this concavity lies the biconcave, clear, apical bodv. The 
