Morphology of Organs. 153 



spacious in the earthworm and in the frog, much reduced in 

 anodon and the snail, more reduced still in Astacus. 



The ccelom can be distinguished from other spaces, such as 

 the hffimocoel, by a number of characters. In the first place the 

 mode of its development already sketched out ; in the second 

 place, when it is at all spacious it envelops more or fewer of 



EPIBLAST 



'^S'fi'/TONEAL FUNNEL 



Fig. 73. — Diagrammatic transverse section of Earthworm, to illustrate some of the 

 characters of the ccelom. (After Goodrich.) 



N, NEPH, nephridia. Beneath the central gut are the generative cells hudded off frOQl 

 peritoneum of septum (not shown)._ The dark line surrounding the gut is the 

 splanchnopleuric peritoneum. Peritoneal funnel represents (diagrammatically) 

 oviduct or sperm duct. 



the organs of the body. In the earthworm all the organs of the 

 body lie within the ccelom, or — to speak more accurately — they 

 are invested by its walls. A glance at Fig. 153 will make this 

 understood. The proper epithelium of the ccelom closely invests 

 the intestine, nephridia, blood-vessels, etc. In anodon (Fig. 

 30, p. 65), where the ccelom is reduced to the pericardial cavity, 

 the heart and a section of the intestine are enclosed by this ccelom 

 in the same fashion. The ccelom of the crayfish (Fig. 25, p. 48), 



