224 PSEUDOBONELUA, A NEW ECHIUROID GENUS, 



large, clear cells, having pseudopodial processes projecting into 

 the lumen in a manner somewhat like that figured by Ikeda 

 (1907, p. 10, PI. 2, fig. 17). The digestive tract in Pseudobonellia 

 appears to be the most degenerate so far known to occur in 

 Bonelliidce, as it consists of a minute spheroidal body, reminding 

 us of one of the fragments figured by Ikeda (1907) in the male 

 of B. miyajimai, in which there occur a large number of separate 

 closed vesicles floating in the body cavity. 



A few, highly-refracting, rounded cells are constantly present 

 in the ccelome, and are probably to be regarded as representing 

 chlorophyllous cells such as are described from the male of B. 

 viridis. The posterior nephridia could not be detected, owing, 

 at least in part, to the extremely small size of the organism. 



The greater part of the remainder of the anterior part of the 

 body cavity is filled with sexual elements. Two vesicula? 

 seminales occur. These are very short, prominent vesicles, or 

 rather sphei - es, usually so dilated with mature sperms that it is 

 impossible to make out the structure of their extremely thin 

 walls. From the inner side of each of these vesicular, a very 

 delicate short vas deferens is given off', travelling forwards and 

 outwards to open independently to the exterior ventrolateral!}- 

 at a little distance behind the anterior extremity. 



The sperms are minute, tailed cells, with rod-like heads. Their 

 formation is different from that of the ova; similar masses of 

 central ("spermatophores") and peripheral cells are formed, 

 but they lie in the anterior dilatation of the body cavity. Sperms 

 do not arise directly from the central cell, but by modification 

 of the peripheral cells. The central cell does not grow very 

 large. When the sperms are full)' developed, they separate from 

 it. Numerous "sperm spheres'" can be seen within the anterior 

 coelomic dilatation. 



It has already been mentioned that the epidermis of the pos- 

 terior third or half of the male is greatly modified. The cells, 

 instead of being small and more or less cubical, become long and 

 irregular, with spaces between them (Plate xi., figs. 23, 24;. Some 

 appear to be branched at the extremity, but this effect is pro- 

 bably given by the irregularities of shape of adjacent cells. The 



