120 University of California Publications. [zoology. 



cells. These are in groups of darkly staining nuclei, soipetimes 

 arranged in large numbers around a central mass of cytoplasm, 

 very frequently in groups of four nuclei imbedded in a mass of 

 cytoplasm. (PI. XII, Fig. 7, tet, and Fig. 7a.) The individual 

 members of these tetrads consist sometimes of solid masses of 

 chromatin, sometimes of an outer layer of chromatin surrounding 

 a vacuole. Whether vacuolated or not, these probably represent 

 stages in the development of spermatozoa — a development which 

 apparently proceeds no further. Without making an exhaustive 

 study of the spermatogenesis, it is, of course, impossible to 

 state positively that degeneration of the testis occurs at this 

 stage in the development of the sperm cells, and such a study 

 lias not been made; but in view of the evidence adduced, the 

 suggestion that the testis docs thus degenerate is worth 

 consideration. 



In examining branches of male colonies in which regeneration 

 is taking place, the quantity of degenerated material in each 

 zocecium is uuusually large as compared with that found in 

 other bryozoa. Such a mass of material is shown in Fig. 6, 

 which repi'eseuts a section of a zooecium containing a small 

 regenerating polypide (re. pd.) and the remains of a degenerated 

 polypide, the former occupant of the zocecium (b. b.). In this 

 "bi^own body" two portions can be distinguished, a round, some- 

 what homogeneous mass representing the tentacles and alimentary 

 canal of the degenerated polypide (dc pit.), and a long, tapering 

 mass extending almost to the base of the zocecium representing, 

 perhaps, the degenerated testis (de. tes.). This latter occupies 

 the position of the testis and closely resembles it in appearance, 

 both of the whole mass and of the individual groups of cells, 

 among which the tetrads, both vacuolated and non-vaeuolated, 

 can lie detected. 



Comparing the early regenerating stages of male and female 

 colonies, the quantity of material in the "brown bodies" in the 

 latter is smaller than that in the male, and represents the degen- 

 erated polypides only. Each is at first a homogeneous mass 

 which later disintegrates more or less, and falls into the base of 

 the zocecium. In the later stages, when the regenerated polypide 

 has attained its full growth, the difference in appearance of the 



