178 



BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Lamellibranclis, tlio inusolos of tlio foot of Gastropods (K. S: II., Fig. 

 5oG, s. m.), and the lymph glands and spleen ot Vertebrates (^M., p. 414). 



The reverse process to the aggivgation of mesenchymatons cells is 

 their Dispeisal, and this has probably been brought about by the 

 opposite cause to that producing aggregation. Since, however, this is 

 a process taking })lace in a protoplasmic mass, its consideration must 

 be deferred. (See page 104.) 



We have been considering the different forms into which mesenchy- 

 matons elements aggregate themselves in the formation of one body ; it 

 now remains to consider the processes taking place between mesenchyme 

 and other protoplasmic bodies. Of those processes I recognize at present 

 four, viz. : the attachment of mesenchymatons cells to a body, following 

 their migration thither ; the eucapsuling and interpeneti'ation by a mass 

 of mesenchyme ; transportation by meseuchjme ; and absorption by 

 mesenchyme. 



^^n.9fem»re». 



Fig. 6. 



Fig. 



4. Jftachment of ^ft•$enrhf/me to another body. This process occurs 

 in the vniion of the muscles of Lamellibranchiata. Annelida. Crustacea, 

 and Rryozoa (Figure 6) to the hard parts of these animals, and of ten- 

 don to bono, in Vertebrates. 



r>. Investment and In/erpenetration. ht/ Mesenchyme, of a mass — cither 

 some other organ of tiie body or a foreign substance, like a parasite — is 

 a not uncommon process. Especially marked is this process in the 

 Tunioata (Figure 7), where migrating follicle cells encapsule and finally 



Fisr. 6. Sections through the body w.«jll of the Bryozoan, P.iludicell.i ; {a) younsr, 

 {h) .ndiilt ; illustr.Hting the process of attachment of niesencliyniatous nuiscles to the 

 cuticula. 



Fisr. 7. Section of the Erorni dissk of Pyrosoma. showing migrating follicular colls 

 surroundinsr tlio bl:i.*tomercs. (See K. i II.. Fig. 771.) 



