6 PROCEEDINGS OF THE NATIONAL. MUSEUM toix,76 



dorsal region is highly muscular (fig. 5) ; moreover, in this part large 

 lacunae are found which are connected with the one which runs along 

 the ventral surface of the mantle. 



The testes (fig. 5) are found in the dorsal part of the visceral mass, 

 in the region below the stalls. They consist of more or less straight 

 tubes which are directed parallel to the median plane. Surrounding 

 the testes there are lacunae of rather large size. The male genital 

 openings could not be found in the sections, as the posterior part of 

 the testes is rather indistinctly visible. In common with all other 

 organs, the testes have a comparatively large size; their diameter 

 amounts to 1 mm approximately in some parts. 



The colleteric glands have a much more complicated structure 

 than those of the other Peltogastridae. They are at each side of the 

 median plane, not far from the stalk; their larger diameter amounts 

 to 10 mm approximately. The lumen of the glands is rather wide, 

 projecting from the center outward as a number of diver ticules 

 which in turn give rise to smaller divisions toward the periphery 

 of the gland (fig. 6). The epithelium of these glands consists of a 

 double layer of rather high cells, which are surrounded externally by 

 a thin muscular layer. At various points the latter is connected 

 with the muscles which traverse the visceral mass. The colleteric 

 glands contain a rather irregular mass of secretion (for the sake of 

 clearness omitted in the figure) in which no distinct structure can 

 be found. x\n opening of the glands on the periphery of the visceral 

 mass could not be detected, but at the proximal side of the glands 

 there is a large opening, constituting the passage for the ripe eggs 

 into the glands. By their highly complicated structure the colleteric 

 glands of Briarosaccus form one of the generic peculiarities separating 

 the genus from the other Peltogastridae. 



The specific characters of Briarosaccus callosus may be derived 

 «dth sufficient accuracy from the details of the chitinous coverings 

 of the external and internal surface of the mantle. As might be 

 expected, these parts also are characterized by their thickness and 

 solidity. 



The external cuticle of the mantle (fig. la) consists of two layers, 

 owing to the fact that the cuticle is in the process of ecdysis. One 

 might think that the two layers had developed by fission of the 

 originally simple external cuticle, but as both of the two layers at 

 their upper surface possess the characteristic small excrescences 

 described below, we have here a formation of a new layer under the 

 old external cuticle. These two layers of the cuticle, both with their 

 characteristic excrescences, have been found in different Sacculinidae 

 (Boschma, 1927) ; and the phenomenon, therefore, is not at all uncom- 

 mon among Rhizocephala. Both of the layers of the external cuticle 

 possess at their upper surface numerous small slender papillae (fig. 

 76), which have a length of about 9/x. Those of the outer layer are 



