ix ENTEROPNEUSTACCELOMIC SAGS 571 



digestive tract only in those species of Pti/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 liver-caeca. 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 cteca is, as a 

 rule, much folded. 



In Glandiceps Hacksii, 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, Glandiceps Hacksii, Balanoglossus Kowa- 

 levskii, and B. Merschkovskii (but not in Pfychodera 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 Hacksii three pairs, and Balanoglossus Kowa- 

 levskii 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 efferent 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 Ccelomie Sacs and the Body Musculature. 



We here use the expression coelomic sacs rather than ecelomie 

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



Five ecelomie 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 eoelomic sac. 

 The collar contains two paired eoalomie sacs. 

 The trunk contains two paired eoelomie 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 blastocoel of the larva, with the exception of 

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

 be described later. 



In each coelomic 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 coelomic sacs are paired, i.e. in the collar and the 



