COMPARATIVE ANATOMY. 39 



noted in these same organs. It thus becomes very probable that they aid in the 

 removal of waste matters, and as noted on page 169 the fact that the male and 

 female glands are identical in form and structure indicates that they play no 

 especially important part in the egg-laying process, merely conveying the ova 

 from the pericardium to the exterior. In the Neomeniina there are certain indica- 

 tions that the coelomoducts do not serve as kidneys, and the fact that they are 

 non-glandular in immature individuals points also to their non-excretory character. 



In other parts of the body of several other species of Solenogastres there are 

 organs of widely different character which are believed by various authors to 

 hold the office of excretory organs. These include a number of structures which 

 are in close proximity to the cloacal wall or are modifications of it. Among 

 them are anal, preanal, or b3'ssus (improbable) glands probably- not in all cases 

 homologous and evidently in some species playing a part in the process of repro- 

 duction, especially where they are muscular, vesicular invaginations of the 

 cloacal wall. Pruvot described a mass of spongy, glandular cells in Myzomenia 

 hanyidcnsi^, forming a low elevation on the floor of the cloacal cavity, and con- 

 taining yellow granules similar to others of larger size in the free cells of the 

 underlying tissue. The supposition is that these last named elements are 

 leucocytes, which, collecting materials from the blood, pass them to the cloacal 

 wall from whence they are voided to the exterior. Thiele states also that in 

 Proneomcnia neapoUtana there is an accumulation of cells irregular in form, 

 forming a preanal gland between the hypodermis and the somatic musculature. 

 (Similar elements are attached to the cloacal wall, the rectum, and coelomoducts, 

 and others of somewhat like character are found in the intestinal sinus. Their 

 resemblance to chlorogogue cells is marked, and for this reason chiefly they are 

 believed to exercise the same function. Heath also has noted the presence of 

 certain cells, along the ventral sinus of Limifossor talpoideus, whose shape and 

 granular contents suggest the connective-tissue, concrement-bearing elements 

 in the Chitons and other molluscs as noted by Brock. The papillae have been 

 looked upon as glandular bodies by several authors and of these a few consider 

 them to be excretory. On the other hand they may function as organs of 

 special sense (see page 40). 



Respiration to a certain extent probably occurs over the general surface 

 of the body, especially in those species with thin cuticle or where the cuticle is 

 provided with blood sinuses. The ventral groove, as several authors have 

 suggested, certainly permits the interchange of gases. The walls of the atrial 

 cavity, especially the cirri and ciliated folds are believed also to take a share in 



