SOLENOGASTRES. 



355 



The cavity called pericardial (Fig. 277 B) is dorsal to the rectum. The heart 

 projects into it dorsally ; it communicates with the exterior by two tubes the 

 so-called nephridia which are bent on themselves like those of so many Mol- 

 lusca, and open by a common median opening into the cloaca ventral to the anus. 



The animals are hermaphrodite, and the genital glands are paired and 

 tubular; they open posteriorly into the pericardium. 



It is extremely doubtful whether we ought to regard the nephridia as 

 anything else than generative ducts, as they bear accessory organs on their 

 course, and no signs of renal excretory products have been seen in them. 



The development has been partly followed in Danders in. There is an 

 invaginate gastrula and a trochosphere with a velum, but no veliger stage 

 nor shell-gland, nor foot. 



The Neomeniidae have been taken in the North Atlantic and in the 

 Mediterranean. There are 6 genera and about 20 species. 



Neomenia Tullberg, with branchiae, without radula ; Puramenia Pruvot, 

 with branchiae and radula ; Proneomenia Hubrecht, without branchiae, thick 

 cuticle enclosing epithelial papillae ; Ismenia Pruvot, cuticle thin, a pre- 

 cloacal ventral prominence ; Lepidomenia Kow. and Mar., cuticle thin, radula 

 large ; Dander sia Hubrecht, cuticle thin, radula rudimentary or absent. 



Fain. 2. Chaetodermidae. Dioecious Solenogastres without pedal groove, 

 with radula as single horny tooth; nephridia with separate openings; branchiae 

 paired and projecting; gonad median. Body with uniform covering of short 

 spicules embedded in the. cuticle. Hind end of body bell -like, consisting 

 of widely open cloaca, which contains two foliaceous branchiae, the anus and 

 the two openings of the nephridia. 



The nervous system consists of two closely apposed cerebral ganglia, from 

 which arises a stomatogastric commissure with two ganglia, and on each side 

 two lateral cords, the pallia! and pedal, which are 

 joined at intervals by commissures. Posteriorly the 

 pedal joins the pallial, and the single cord thus formed 

 joins its fellow dorsal to the rectum in the supra-rectal 

 ganglion. There are no special organs of sense. 



The mouth is anterior and terminal, the radula is 

 represented by a single horny spine in a pit in the 

 floor of the mouth, the alimentary canal is straight, 

 and the liver is a single ventral caecum directed 

 forwards and opening into the middle region of the 

 alimentary canal. 



The vascular system is much as in the Neomeniidae 

 except that the haemoglobin is in the plasma. 



The nephridia (Fig. 277) resemble those of Neomenia, 

 but they are without accessory genital structures, are 

 more obviously renal in function, and they open 

 separately. 



The sexes are separate. The gonad is a single 



median tube opening into the pericardium, and the genital products pass out 

 by the kidneys (Fig. 277 A}. 



The development is unknown. 



There is one genus with three species ; from the North Atlantic, the Arctic, 

 and the Pacific Oceans. 



Chactoderma Loven. 



a 



Flo. 278. Chactoderma 

 ititiiluJiim (from Per- 

 rier). anterior end ; 

 b posterior end. 



