IX ENTEmPNEUSTA—G(ELOMIG SAC'S 571 



digestive tract only in those species of Pii/chodera and Schizocardium 

 in which it gives off on each side dorsally a row of finger- or wedge- 

 shaped outgrowths, which push out the body wall in such a way 

 as to form the above-mentioned livep-eseea. The aperture of each 

 caecum into the alimentary canal is a narrow transverse slit. Food 

 never passes into the liver-caeca. The capillary network is exceedingly 

 close in their walls, and the intestinal epithelium of the caeca is, as a 

 rule, much folded. 



In Glandiceps Hachsii, an accessory intestine occurs in the hepatic 

 region : this is a straight canal, ca. 6 mm. long, which branches off 

 from the median dorsal surface of the intestine proper about the 

 middle of the region, and again enters it at the posterior end of the 

 same region. 



In Schizocardium brasiliense, Olandiceps Hachsii, Balanoglossus Kowa- 

 leislii, and B. Merschkovskii (but not in Ptychodera and not in B. Kupfferi, 

 and B. canadensis) paired intestinal pores, leading outward dorsally, are 

 found in the most anterior hepatic region, or in the region immediately 

 in front of it, intercalated between it and the afferent intestine. Schi. 

 brasiliense has one pair, Gl. Hachsii three pairs, and Balanoglossus Kowa- 

 levshii four to six pairs of such pores. They emerge mediad of the 

 submedian line, and may be provided with cilia and with sphincter 

 muscles. 



F. The hepatic intestine is followed by the efTerent section, 

 which gradually passes into the narrower rectum, this in its turn 

 opening outward through the anus. Where, in this section, a proper 

 musculature is found, it is very weakly developed. 



VI. The Coelomic Sacs and the Body Musculature. 



We here use the expression coelomic sacs rather than eCBlomic 

 cavities, the former implying that they have walls of their own. 



Five coelomic sacs occur in the body of an Enteropneustan, these 

 being divided among the principal regions of the body as follows : — 



The proboscis contains one unpaired coelomic sac. 

 The collar contains two paired coelomic sacs. 

 The trunk contains two paired coelomic sacs. 



The coelomic sacs fill up almost the whole of the space between 

 the intestinal epithelium and the body epithelium, i.e. the seg- 

 mentation cavity or blastoeoel of the larva, with the exception of 

 a system of spaces, serving as the blood vascular system, which will 

 be described later. 



In each ccelomic sac there can be distinguished, at the least, a 

 visceral wall in contact externally with the intestinal epithelium, and 

 a parietal wall, in contact internally with the body epithelium. 



Where the ccelomic sacs are paired, i.e. in the collar and the 



