RELATIONSHIP OF AMMOCCETES TO OSTRACODERMS 333 



m. ph . ._ il 



Cor- - 



In Fig. 132, B, I give a specimen of this tissue stained by osmic 

 acid; in Fig. 132, A, I give a drawing of ordinary muco-cartilage 

 taken from the plate of the lower lip; and in Fig. 133, A, a modifi- 

 cation of the muco-cartilage taken from the velum, which shows the 

 formation of a tissue in- 

 termediate between ordi- 

 nary muco-cartilage and 

 this branchial fat-tissue. 



Further, in fully-grown 

 specimens of Ammoccetes, 

 in the region of undoubted 

 muco-cartilage, a fatty de- 

 generation of the cells 

 frequently appears, to- 

 gether with an increase 

 in the blood spaces, — the 

 precursor, in fact, of the 

 great change which over- mb r 

 takes this tissue soon 

 afterwards, at the time of 

 transformation, when it is 

 invaded by blood, and 

 swept away, except in 

 those places where new 

 cartilage is formed. I 

 conclude, then, that the 



tissue of this vascular 



Fig. 132. — A, Muco-cartilage op Lower Lip 



space was originally muco- (Uc) . mphi musc i e f lower lip; m.sm., 



cartilage, which has de- somatic muscle ; Cor., laminated layer of skin. 



~ ~+~;i .1 „„,•„„ 4-V.„ kp^ B, Degenerated Muco-cartilage op Bran- 



generated during the lire ' _, _ . , , T1 



° chial Region. F., fat layer; P., pigment; 



of the AmmOC03teS. The. ^l, blood-space; N., somatic nerve; vi.br., 



fact that in most cases branchial muscle ; m.sm., somatic muscle. 



undoubted muco-cartilage 



is to be found here and there in this space, is strong confirmation of 



the truth of this conclusion. 



If this conclusion is correct, we may expect that it would be 

 confirmed by the embryological history of the tissue, and we ought 

 to find that in much younger stages a homogeneous tissue of the 

 same nature as muco-cartilage fills up the spaces in the branchial 



in. sra 



