TROPHOrHOEE OF HYDROIDES UNCINATUS (EFPOMATrs). 583 



recent an investigator as Treadwell (43) is of opinion that tliey 

 have such an origin. He, however, did not trace the bands in 

 Podarke beyond a stage when they were represented by a 

 few cells, so he obtained no definite information on this point. 



In Eupomatns it is clear that the anterior ends of the 

 bands never give off cells into the blastocoel as Hatschek 

 has described. They can be plainly observed throughout the 

 course of their growth; they are always a compact mass of 

 cells, clearly distinct from the larval mesenchyme. The larval 

 mesenchyme cells enter into close relation with the cells of 

 the bands, as may be seen in Text-figs. 25 and 26, and in part 

 overgrow tliem, but even in the living condition they cun 

 usually be distinguished. In sections in wliich the fixation 

 has been i-apid they can readily be separated on account of 

 their different stainingproperties — a point thathas been exten- 

 sively used by Meyer in his numerous studies on this question. 



In Eupomatns a large part of the larval musculature has 

 already been laid down before the foi-mation of the bands has 

 taken place, the greater part of this musculature persisting 

 and ultimately forming a very considerable portioii of the 

 adult body. 



Meyer (27) has criticised Hatschek's statement regarding 

 the origin of the mesenchyme in Eujiomatus, and lias 

 expressed himself as being veiy sceptical as to whether cells 

 arise from the anterior ends of the bands. He is of opinion 

 tliat, with more modern technique than that employed by 

 Hatschek, whose observations were restricted, to living 

 material and optical sections, the facts of the case will prove 

 different. He points out that while Hatschek describes the 

 coelomesoblast pole-cells as giving off cells into the blastocoel 

 before they form the bands, he neither figures nor appears to 

 have seen the division of these cells. Torrey (41), in speaking 

 of the resemblance of the ectomesoblast in l\)darke and 

 Thalassema, says, " The striking similarity in the origin of 

 the ectomesoblast in these two forms justifies us, I believe, 

 in supposing that Ave may have the same condition of affairs 

 in Eupomatns where the cleavage is also equal " (p. 226). 



