PYROSOMA -DEVELOPMENT OF THE PROLIFERATING STOLON. 485 



large cells are seen in it which can be recognised as young egg-cells. 

 The rudiment of the genital strand has, in its turn, become abstricted 

 from the genital rudiment (o, h) of the parent (cf. ms, in individuals 

 // and III). 



FIG. 253. A chain of three individuals of Pyrosonw (after SEELIGER). /, youngest, 

 proximal bud ; //. middle and ///, oldest, distal bud (nearly fully developed). />, 

 point at which the eudostyle-process ot the parent enters ; d, endostyle- or entoderm- 

 process ; dc, rudiment of the alimentary canal ; dm, elongate cell-mass ; e, rudiment 

 of the atrial aperture ; eh, elaeoblast ; EC, ectoderm of the parent ; ec, ectoderm- 

 plate of tlit- stolon-rudiment ; Es, endostyle of the parent ; es, endostyle ; /</, ciliated 

 pit; y, ganglion ; h, testis ; hd, intestine ; hz, heart ; i, rudiment of the branchial 

 aperture ; kl, atrium ; ks, gill-clefts ; If, internal longitudinal gill-bars ; Im, lenti- 

 cular phosphorescent organ ; m, stomach ; ms, genital strand ; n, rudiment of the 

 iii-rvons system ; /. ovary (egg-follicle with egg) ; oe, oesophagus ; p, dotted line 

 indicating the boundary of the peribrauchial sacs ; , pc, pericardium; rz, languets ; 

 t, tentacle-rudiment ; v, duct connecting the enteric cavity of the second individual 

 with that of tin- third. 



These two rudiments (those of the entoderm-process and the 

 genital strand) can also be recognised in a transverse section through 

 this region of the body of the parent (Fig. 255). We then also see 

 that the entoderm-process is still accompanied by isolated mesen- 

 chyme-cells (Fig. 254, ms). At the two sides of the process especially, 

 mesenchyme-cells can be seen arranged in two strands (ms). The 



