DAVEXrORT: PROCESSES CONCERNED IN ONTOGENY. 



179 



penetrate between the blastomeres, so that it is difficult to tell which 

 part of the embryo has been derived from the egg and which part by 

 immigration. Compare the 

 origin of the cutis in Echino- 

 derms (K. & H., Fig. 195), in 

 Mollusca (K. & H., Fig. 686), 

 and in Vertebrates (M., Fig. 

 306), and of the intestinal and 

 vascular musculature of Verte- 

 brates (H.-M., Fig. 185). 



All of these processes have 

 this in common, that mesen- 

 chyme migrates to an organ 

 — vessel, layer, or mass — and 

 applies itself closely to it, 

 sometimes even penetrating 

 into the substance of the 

 organ. 



6. Transportation by Mes- 

 enchyme has hitherto been 

 observed in but few cases. 

 The most remarkable instance 

 of this process is found in the 

 Doliolidae, where the buds pro- 

 duced from a stolon are trans- 

 ported over half the length 

 and half the circumference of 

 the body by means of mesen- 

 chyme cells, and are finally 

 deposited, in very regular or- 

 der, on the appendage of the 

 budding individual. (Figures 

 8 and 9.) By similar means, 

 apparently, one end of the 

 funiculus of the Bryozoan Cristatella is transported from the dorsal to 

 the ventral surface of the corni, as I have attempted to show elsewhere. 

 (Bull. Mus. Comp. Zool., XX. 142.) 



Fig. 8. Dorsal view of tlie posterior rart of a large Doliolum "nurse." Shows 

 the buds being transported from the ventral to the dorsal (and posterior) stolon. 

 (See K. & H., Fig. 830.) 



J}or»«/ «/•;•„ 



Fig. 8. 



