CCELOMIC SACS 



of important differentiations and consequent development of new 

 organs, such as genital ducts and renal excretory glands, besides 

 affecting the mechanical conditions of the body-wall and muscles, 

 and the diffusion of chemical products within the body. 



A me 



Fio. 3. — Transverse Sections or 

 Two Stages of the Larva of 



THE BrACHIOPOD AROIOPE TO 



SHOW THE Origin of the Ccelom 

 AS A Pair of Enterooelods 

 Pouches. 



A, younger stage. U, blastopore; 

 j)ii, right cu-loinic pouch continuous 

 witli WK', tlie archenteron. if, later 

 st.nge, the cix-loiiiic jKjUfh (;ir) is now 

 shut oil' from the archenteron, me. ; 

 /(, temporary bristles. (After Kowa- 

 lew.sky, from Balfour.) 



Accordingly we divide the Enterozoa into those in which the 

 sole cavity is the enteron — the Enterocwla — and those in which 

 the crelom is present as an independent second cavity — the Cado- 



Grade B. C(ELOMOC(ELA. 



Grade A. ENTEROCCELA. 



ENTEROZOA. 



1 The two grades wliich I liere call Enteroccela and Coelomoccela are 

 often designated Cadentera and Ccelomata. The word Coclenterata (due 

 to Lewekart, 1848) has been used by some authors. It seems to me that 

 it is legitimate to transpo-se the components of Co?lentera so as to form 

 the word Enterocojla, and we then are able to form a very much better 

 pair to it than is Cudomata (Ilaeckel's term), by coining the word 

 ('(I'loniocada. The contrast of animals whose sole cavity is the enteron 

 or gut-chamber with those which have a ccelom as an essential and dis- 

 tinct cavity is thus clearly expressed. 



The use of the term cnterocol for the cadom itself, and of the word 

 Entcrocadia for a large division of cadomocctdous animals by the 

 Hertwigs n>ay seem to render the conversion of Cadentera into Entero- 

 ccela inconvenient. But the word " enteroc(elous " or " enterocudic " is 

 still quite approj)riate as a description of the early phase of development 

 of the cadom for the very same reason wliich justifies us in calling 

 polyps and medusa^ Enterocada or Cadentera, viz. that we refer to the 

 existence of a cavity which is in origin in the one case, and permanently 

 in the other — a part of the enteron. As to the Hertwigs term " Entero- 



