2 74 I)itrodiiction to Animal Morphology. 



The foot consists of a central, obtuse, cylindrical 

 lobe, hollowed at its base, and two lateral, symme- 

 trical, wing-like epipodia. The organs oi Bojanus are 

 symmetrical, brown, compact, of many follicles lined 

 by gland cells, lying on the rectum ; they open into 

 the hinder part of the mantle cavity, and the right 

 receives the genital duct. 



There are two pear-shaped epipharyngeal ganglia, 

 joined by a long commissure in front of the buccal 

 mass, and behind the pseudo-coUum ; from these arise 

 two pedal commissures, two buccal, two tentacular, 

 and four mantle nerves (inner and outer pair), as well 

 as an azygos mantle-ner\^e. The hypopharyngeal 

 (foot) ganglion is close to its fellow, gives off many 

 (nine) foot nerves, and each has seated on it a sphe- 

 rical, ciliated otocyst containing many rapidly-moving 

 otoliths. A pair of anal ganglia are attached to- 

 gether by a fine thread, and to the epipharyngeal by 

 two filaments. Besides these are two anterior and 

 two posterior sympathetic ganglia, joined by commis- 

 sures, lying on the intestine. There are no eyes, but 

 the animal retracts its foot if exposed to light. 



The long, lobed sex-gland differs in the male and 

 female only in the nature and colour of its contents, 

 being white in the male, red and yellow in the female. 

 It fills the entire (Siphonodentalium) or front (Denta- 

 lium) of the metasoma, and has no accessory organs. 

 The eggs have shells, and form on stalked processes 

 in the ovary ; when impregnated, the yelk rotates, 

 segments, and forms a ciliated gastrula, which elon- 

 gates, and the external cilia form seven complete 

 circlets, the foremost of which dilate into a velum, 

 and the others vanish. On each side posteriorly a 



