78 NICHOLS — SPERMATOGENESIS ONISCUS ASELLUS LINN. [April 4, 



I. Structure of the Male Reproductive Organs. 



The male reproductive organs of the land Isopods are paired and 

 lie on either side of the tubular intestine, occupying almost the 

 entire length of the thoracic region. 



The testis consists of three narrow lobes, which are attached to 

 the body musculature by slight strands of tissue. These lobes are 

 distinct from each other and open successively into the anterior 

 expanded portion of the vas deferens (Fig. i). Posteriorly the 

 vas deferens narrows to a more slender tube, which joins its fellow 

 of the opposite side and opens through the penis, which is unpaired 

 and is said by Gerstaecker (1882) to be an outgrowth from the 

 seventh thoracic segment. It is enclosed by the modified internal 

 lamellae of the first abdominal appendages (Fig. i). 



Sections of the vas deferens (Fig. 3) show its expanded portion 

 to be lined with cells of large size, which possess prominent 

 spherical nuclei. The nucleus is sometimes surrounded by a clear 

 space, varying somewhat in size. The chromatin is in the form of 

 closely crowded granules. Between these are sometimes other 

 granules, which with the iron haematoxylin stain are less deeply 

 colored, and with Bordeaux red and Delafield's hsematoxylin take 

 a red tint. The periphery of the latter is usually darker in color. 

 The surrounding cytoplasm is filled with particles of a rounded 

 shape, which take cytoplasmic stains (Fig. 4a). In one prepara- 

 tion the cytoplasm of these cells was filled with particles, not 

 rounded in shape but thread-like, and taking a very dark stain with 

 iron hsematoxylin. The chromatin consisted of granules of varying 

 size, which appeared lighter in the centre and possessed a darker 

 margin (Fig. 4^). I do not know whether there is any connection 

 between the particles within the nucleus and those without ; the 

 subject might possibly repay further research. The appearance of 

 these cells suggests strongly that they have a secretory function ; no 

 doubt the fluid which bathes the spermatozoa is produced by them. 

 They are more abundant at those places where the follicles open 

 into the vas deferens and grow more scarce in the region where the 

 narrow portion of the vas commences (Fig. 3). Between them are 

 to be seen nuclei of smaller size, whose chromatin is not so 

 distinctly and regularly granular. These lie in a cytoplasmic reti- 

 culum of a coarse mesh, without well-defined cell boundaries and 

 containing no granules. This tissue apparently forms a supporting 



