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 cehs. 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 



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I 



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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 spermatocytes; 

 Fig. 4, spermatids; Fig. 5, spermatozoa. Fig. I,x770; Figs. 2-5, x 1050. 



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 body. The 



