SALPA — DEVELOPMENT OF THE ORGANS IN THE BUD. 511 



origin of these organs. According to Brooks, the muscle-tubes give 

 rise to the body-musculature. We may no doubt assume that the 

 paired segments of these tubes spread out on either side of the bud 

 and thus yield muscle-plates, which become fenestrated and then 

 break up into the muscle-hoops. 



The rudiment of the genital organs is yielded by the genital strand 

 (Figs. 264, 265, r/). We have already seen (p. 497) that young egg- 

 cells can early be i*ecognised within this strand. These at first are 

 very plentiful, but many of them disintegrate later and seem to serve 

 as food for the developing eggs. When the genital strand is ready 

 to break up into segments, the eggs become arranged in such a way 

 that only one occurs in each division. The smaller peripheral cells 

 of the genital strand yield the egg-follicle, the oviduct and (according 

 to Seeliger) probably also the rudiment of the testis. Even in 



-v* 



A~" 



Fig. 278. — Chain-form of Saljoa democratica-mucronata from the distal part of an 

 advanced stolon (after Seeliger). c, atrium ; e, atrial aperture ; eb, elaeoblast ; 

 es, endostyle ; fg, ciliated pit; g, ganglion ; A. rudiment of testis; hf, connecting 

 process ; hz, heart ; i. branchial aperture ; in, intestine ; k, gill ; m, stomach ; 

 oc, eye ; od, oviduct : oe, oesophagus ; ov, egg-follicle ; j>/;., pharynx. 



early stages, it is evident, in cross-sections through the stolon, that 

 a group of cells becomes detached in each segment from the lower 

 part of the genital strand, and this probably is to be regarded as the 

 rudiment of the testis (Fig. 264, c, h). 



The rudiment of the genital organs originally lies at the posterior 

 end of each bud. Later the egg-follicle shifts farther forward on the 

 dorsal side and then lies above the intestinal loop in the dorsal median 

 line. From this point the oviduct turns to the right with an S-shaped 

 curve and becomes connected on the right side of the body with the 

 epithelium of the atrial cavity (Fig. 278, ov and od). The watch- 

 glass-shaped rudiment of the testis (h) remains longer at the posterior 

 end of the body curved round the posterior end of the intestinal loop. 

 At a later stage it breaks up into separate tubes which unite to form 



