138 



S. GOTO. 



its external pore, while the vas deferens opens between the two sets 

 of chitinous armature just described. 



Owing to scantiness of specimens I have not been able to 

 make sagittal sections of M. truncata and M. reticulata; but comparing 

 the preparations in toto of these species with those of others, the pre- 

 sence of the genital atrium can hardly be doubted, and the general 

 disposition of its parts is, I beUeve, similar to that found in other 

 species. In M. truncata the chitinous armature of the atrium consists 

 of twenty long, hollow rods, slightly curved twice in opposite direc- 

 tions (PI. II, fig. 2). They are elliptical in cross-section (fig. 2, c), 

 and although on a surface view they appeared of unequnl lengths, as 

 represented in the figure, I believe this is owing to the fact that some 

 were looked at more obliquely than others. They are arranged in a 

 circle, but the series is broken in the median line on the dorsal side. 



The genital atriuna of M. reticulata and Azine abenans are very 

 similar to each other, the internal surface being in both the species 

 covered with spines, and the mesenchyma around the atrium being 

 transformed into the refractive connective tissue so often mentioned 

 already. The form of the spines are, however, different in the two 

 species, those of A. aberrans being simply conical and slightly curved, 

 while those of M. reticulata are exactly similar to those that are present 

 in the terminal portion of its vas deferens, and consists, as already 

 described, of a hemispherical basal and a straight, spinous, distal 

 portion (PI. V, fig. 6). In Axine heterocerca the genital atrium is an 

 irregular, tolerably spacious cavity, and is surrounded by a refractive, 

 fibrous connective tissue somewhat similar to that just mentioned 

 in M. reticulata. Unlike that, however, it stains but slightly 

 (PI. VIII, fig. 3), and in fact its occurrence here appears to me 

 as a step towards the formation from the usual form of the mes- 

 enchyma of such refractive tissue as has been described above in 



