The spermatogenesis of Peripatus (Peripatopsis) balfouri. 283 



somewhat iu size, aud usualh* are spherical; but sometimes they are 

 larger, and then rod-shaped or oval in outline (Fig. 239); all these 

 forms may occur in the same cell. And in the same cell, with iron 

 haematoxyline or satfranine-violet, they may show all color gradations 

 from an unstained condition to deep blue or violet. The most in- 

 tensely stained spherules appear to be limited to those cells which 

 are most irregular in form. Such different staining intensities un- 

 doubtedly represent different stages in their formation, different 

 chemical states. In the cell in which they were most carefully 

 examined, it was found that in general the most deeply-staining lay 

 nearest the nucleus, the lighter-staining at the periphery of the cell. 

 Now if it be the case that these yolk globules are derived from, or 

 in some way acted upon by, the nucleus, which is probable even 

 though I was unable to find any within the latter: then we might 

 conclude that the deeply-staining globules lying nearest the nucleus 

 represent earlier stages, and that the lightly-staining ones are later 

 stages which have been carried to the periphery of the cell. 



I have considered these cells as providers of yolk substance for 

 the spermatogonia, since the yolk globules in the most peripheral 

 spermatogonia are similar in size, form and color relations to those 

 in the nurse cells (Fig, 1, Plate 19). Sometimes also yolk spherules 

 are found in the space between the two muscle layers, which would 

 speak for their migration out of the nurse cells. The nurse cells 

 themselves are possibly derivatives of the haemolymph cells {B. (7, 

 Fig. 234, Plate 23), though this point can be proved only on embryo- 

 logical examination: the haemolymph cells are much smaller, but 

 contain irregularly lobular nuclei and different stages of deeply-staining 

 globules which have a close resemblance to the yolk globules of the 

 nurse cells. It would seem probable that the nurse cells might derive 

 their yolk substance from the haemolymph cells; or perhaps more 

 probable, that the nurse cells are haemolymph cells which have ap- 

 plied themselves to the surface of the testis, there increased greatly 

 in volume, and so come to be providers of nutritive substances for 

 the germ cells. On account of their position on the external surface 

 of the testis they cannot be ascribed any genetic relation to the 

 spermatogonia, so that in respect of their origin they cannot be homo- 

 logized with the nurse cells of the ovaries of Insects. 



b) The Fibre-cells of the Testis. 

 Within the testis are long, branching cells, which course more or 

 less radially from the inner surface of its sheath to the axial lumen 



