476 



INVERTEBRATE MORPHOLOGY. 



m bundles, two of 

 are situated dorsally, 



ven- 



Beneath the thin cuticle is situated the hypodermis, and 



beneath this a well- developed 

 dermal muscular system re- 

 calling that of the Annelida, 

 being composed of an outer 

 layer of circular muscles, be- 

 low which are diagonal fibres, 

 and below these again strongly- 

 developed longitudinal muscles 



bundles, 

 which 



two laterally, and three 

 trally. In addition to these, 

 dorso - ventral bands occur 

 passing across the ccelom and 

 dividing it into three chambers, 

 one median and two lateral, 

 and special muscles are also 

 present for moving the limbs. 



The coelom is tolerably 

 capacious and consists of two 

 portions. The larger portion 

 is divided by partitions into 

 several subordinate cavities 

 (Fig. 220), and is lined through- 

 out by a peritoneal epithelium 

 which covers the various or- 

 gans. From it are, however, 

 separated certain cavities with 

 definite walls, Avhich stand in 

 relation to the uephridia and 

 the reproductive organs and 

 will be spoken of in connection 

 with these organs. A heart 

 (Fig. 220, Ji) of a tubular form 

 extends throughout almost the 

 entire length of the body, lying 

 in a pericardial space (Fig. 220, pc] incompletely separated 

 from the rest of the coelorn by a fenestrated transverse par- 



FIG. 219. FIGURE SHOWING THE 

 STRUCTURE OF A FEMALE Peripatus 



(from HERTWIG). 



rt = anus. 

 at = antennae. 

 bm = ventral nerve-cord. 



d = intestine. 

 go = opening of reproductive organ. 



o = ovary. 

 og = brain. 



p = pharynx. 

 sd = "slime-glands. 



so = nephridia. 



sp salivary glands. 



tr = tracheae. 



u = uterus. 



