Further Studies on Reproduction in Sagitta. 293 



winding fertilization canal (c). The eggs of Sagitta elegans 

 have a much thinner membrane than those of Sagitta bipunctata. 

 In this figure one sees the usual conditions in the region of attach- 

 ment of an egg which is nearly ripe, — the ends of the surrounding 

 cells of the oviduct wall stain more deeply, and one also finds the 

 stain showing between cells, simulating fibers. The nuclei of two 

 cells adjoining the outer connecting cell have perfectly black 

 nuclei, probably indicating degeneration. In Fig. 43 is shown the 

 place where an egg has broken away without making its way into 

 the oviduct. The cells surrounding the torn connecting cell (a) 

 stain almost perfectly black on a well differentiated slide. It 

 is also true that when an egg is passing from the ovary into the 

 oviduct the cells on the border of the opening through which the 

 egg is passing stain deeply, indicating some change connected 

 with the ripening of the egg. In Sagitta inflata the nuclei of the 

 connecting cells stain darker, and it is more difficult to say how early 

 degeneration begins. Fig. 44 shows the two connecting or acces- 

 sory cells of a comparatively young egg and Fig. 45 of an older 

 egg. In both figures sections of the fertilization tube (c) are 

 seen. 



The 'Besondeke Korper' in the Primary Germ Cells 



My material does not include the stage in which the ' besondere 

 Korper ' divides in the sixth segmentation mitosis, which gives 

 rise to the two primary germ cells, but I find the remains of this 

 body in many sections of young gastrulse. In Sagitta bipunctata 

 they are very often conspicuous in a stage where the germ cells 

 are still buried in the gastrula wall (Fig. 46 k). In this particular 

 case these bodies were as deeply stained as in the earlier stages. 

 When the two germ cells are in mitosis, I find only less deeply 

 staining fragments (Fig. 47 a and 6, k) . Likewise in the 4-germ 

 cell stage I find some fragments (Fig. 48). Corresponding bodies 

 are found in Sagitta inflata and Sagitta elegans, but in both they 

 are less conspicuous. Fig. 49 is an early 2-germ cell stage of Sag- 

 itta elegans, showing one gray mass in cell a, none in 6 ; in the next 

 section there were two more such masses in a, but none in h, indi- 



