lO 



In my opinion both forms are to be classed in one species, the one point of difference 

 not outbalancing the very important resemblance. 



This species is doubtless closely allied to Proneomenia Weberi. The shape of the body, 

 the integument, the cloaca-ducts with appendages, the heart and the copulation-spicula present 

 many points of conformity; buth the length-index, the structure of the radula and the cloaca 

 differ in many respects. 



The principal points of difference from the type of the genus are found in the structure 

 of the radula and of the cloaca-ducts, and in the presence of copulation-spicula. 



o- 



Proneomenia sp. (PI. II hgs 57 — 59). 



Stat. 87. o°32'S., ii9°39'.SE., near Palos-bay, W. Celebes. 655 M. In mud. i Specimen 

 (fragment). 



A fragment of i mm. high and broad. The appearance of this posterior extremity is like 



that of Proneomenia Weberi. The specimen must be mentioned on account of the structure ot 



the cloaca-ducts. Fig. 57 represents a reconstruction of the interior organs. Regarding this the 



following should be noticed. The cloaca is a simple cavity, without proximal offsets. Gradually 



its slightly ciliated epithelium changes into the higher strongly ciliated epithelium of the rectum. 



Laterally the cloaca is continuous with two small coeca {a). The course of the cloaca-ducts is 



normal. The portion, running proximally carries cilia, but is without the vesiculae seminales ot 



the foregoing species. Both parts of the cloaca ducts, proceeding distally, remain separated 



(fig. 59). They do not unite into the precloacal organ. The epithelium is rather cubical and not 



ciliated. Where they curve, the cloaca-ducts are continued into the coeca b^ uniformly structured ; 



other appendages are absent. Shortly before their opening out into the cloaca, both ducts 



coalesce, but the ur.paired portion is very small (0.05 mm.). Of the well-known tissue of the 



precloacal organ nothing is perceptible. In other forms this arrangement also obtains in more 



or less degree. Thiele observed (8) in Proneomenia neapolitana that the cloaca-ducts coalesce, 



the epithelium of the united part remaining low, not being glandular either. In his opinion 



there is some relation between this condition and the animal's immaturity. In my specimen the 



genital glands are small and no production of genital material takes place. Here also the slight 



development of the cloaca-ducts might go together with the immaturity of the animal. This 



also Kow.\LEWSKY and Marion noticed for Lepidomenia hystrix (2) and Pruvot for Proneomenia 



vagans (4). However Thiele makes mention for the mature Notomenia clavigera (9) of two 



glandular cloaca-ducts opening to the exterior separately, but not into the cloaca. For Strophomenia 



Lacazei Pruvot describes (10) two fully developed cloaca-ducts with appendages, opening out 



severally into the cloaca. The possibility of the ducts remaining separated in this case too is 



not excluded, but it is also possible that wc have to do with a young specimen. The structure 



of the cloaca points towards that of Proneomenia longa, though there is not complete similarity 



between the two. Here too the cloaca-spicula are wanting but perhaps they only developc in 



maturity. Further, to the right and left, a copulation-spiculum is present, cross-shaped or more 



triangular, with a delicate culicular sheath. Very distinct are the dorsal and ventral blood-sinuses. 



