contain eo-o-s formed at the meclian wall and spermatozoa formed at the lateral wall. The 

 structure of the efferent canals fully corresponds to that of Proneomenia Weberi (fig. n). 

 Only the cloaca is of a simpler structure (cf. figs 5 — 9 with figs 30 — 35). Fig. 5 corresponds 

 to fig. 30 ; here also at b is an invagination of the body-wall, carrying spicula which here are 

 curved, whereas the papillae are broader and the vesicular knob is much less visible. Only 

 the precloacal organ opens out more proximally, this being therefore not visible is fig. 30. 

 The following figures 110 Jonger correspond. Here we observe that the cloaca does not form 

 the proximal coeca a, c and <ƒ, but only «, into which merges the rectum, its epithelium having 

 been noticed above. The wall of the cloaca is built up of ciliated cylindrical epithelium. More 

 proximally this changes into a multicellular epithelium (fig. 38); the cells are glandular and 

 accumulated, the wall containing therefore in a more or less degree papillae ; the whole gives 

 the impression of glandular epithelium with cilia. Along the median part of the dorsal wall 

 runs a strongly ciliated band of epithelial cells. At the lateral cloaca-walls the epithelium is 

 different (fig. 39) : regularly granular, ciliated, strongly staining cells alternate with more 

 transparent cells, carrying no cilia. This tissue strongly resembles that of the cloaca-wall of 

 Chaetoderma (Wirén 6 a , Taf. \T fig. 9), though with respect to-this absolute certainty cannot 

 be obtained. The possibility of this tissue being also present in this animals cloaca-wall should 

 of course not be excluded, whilst in the other Xeomeniidae it is only to be found in the wall 

 of the precloacal organ, this being here also the case. The two copulation-spicula are built as 

 in Proneomenia Weberi. 



The structure of the heart may be compared with that of Proneomenia Weberi. On 

 both sides of the median walls of the pericardial offsets, part of the wall is also invaginated, 

 which invaginations fuse into one atrium. In this atrium the original doublé origin may very 

 easily be recognized (fig. 36). Here too the ventricle is an invagination of the dorsal pericardial 

 wall, of very small extent first, but larger more proximally. The atrium is in continuity with 

 the ventricle, the latter being still very small; here are also two atrio-ventricular openings, both 

 of them closed by a little sphincter. Only one of the openings is visible in fig. 36. The blood- 

 sinus, with the exception of the dorsal one, are very clifficult to follow. 



The length of the second specimen is i~ mm.; its diameter 1 mm.; the length-index 

 therefore 37. The colour is not yellow-white but light brown. For the rest the appearance is quite 

 the same as that of the first specimen. The structure of the interior also coincides. The radula-sac 

 is very distinct (fig. 37). The radula-teeth are still delicate and curved in the sac ; in cutting 

 they are therefore generally touched at two pointe. The formation takes place simultaneously 

 with that of the basal membrane, which does not differ from the teeth in consistency. 



The only real difference between the two specimens lies in the copulation-spicula. Fig. 

 40 gives a section through the hinder part of the body and may be compared with a section 

 between figs 32 and 33. Here it is seen, that not one copulation-spiculum is found on either 

 side, but that there are several : 5 to the left and 8 to the right. They are small spicula, 

 surrounded by a thin cuticula and sheath, built up of cubical epithelium. Each is provided with 

 its own muscular bundies. They open out into the cloaca at the ventral wall, before the cloaca 

 opens to the exterior. 



SIBOGA-EXI'EDITIE XI.VII. 



