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. 



-" me 



FIG. 3. TRANSVERSE SECTIONS OF 

 Two STAGES OF THE LARVA OF 

 THE BRACHIOPOD ARGIOPE TO 

 SHOW THE ORIGIN OF THE CCELOM 

 AS A PAIR OF ENTEROCCELOUS 

 POUCHES. 



A, younger stage, bl, blastopore ; 

 pv, right ccelomic pouch continuous 

 with me, the archenteron. S, later 

 stage, the ccelomic pouch (pv) is now 

 shut off from the archenteron, me ; 

 b, temporary bristles. (After Kowa- 

 lewsky, from Balfour.) 



Accordingly we divide the Enterozoa into those in which the 

 sole cavity is the enteron the Enterocoela and those in which 

 the ccelom is present as an independent second cavity the Ccelo- 

 mocoela. 1 



Grade B. CCELOMOCCELA. 



Grade A. ENTEROCOELA. 



ENTEROZOA. 



1 The two grades which I here call Enteroccela and Coelomoccela are 

 often designated Ccelentera and Ccelomata. The word Coelenterata (due 

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

 it is legitimate to transpose the components of Ccelentera so as to form 

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

 pair to it than is Ccelomata (Haeckel's term), by coining the word 

 Cielomoccela. The contrast of animals whose sole cavity is the enteron 

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

 tinct cavity is thus clearly expressed. 



The use of the term enteroccel for the ccelom itself, and of the word 

 Enteroccelia for a large division of ccelomocoelous animals by the 

 Hertwigs may seem to render the conversion of Ccelentera into Entero- 

 coela inconvenient. But the word " enteroccelous " or " enteroccelic " is 

 still quite appropriate as a description of the early phase of development 

 of the ccelom for the very same reason which justifies us in calling 

 polyps and medusae, Enteroccela or Ccelentera, 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- 



