590 



Transachons. 



Sense-organs. Plate XXVIII, fig. 4. 



Distributed all over the external surface of the body are tactile organs, 

 as evidenced by the fact that when a part of the epidermis is stimulated 

 the creature withdraws that region, and so adjusts itself to its environment. 



I looked for an otocyst, but was unable to find one. 



A pair of eyes is present. Each is situated on the anterior region of the 

 head, well to the side, and symmetrically placed with regard to the other 

 (Plate XXVIII, 4 ; e). I discovered them by cutting a series of sections 

 through the head of a young specimen. Each appears to lie imbedded in 

 the muscles of the cephalic wall, at the base of a little depression which 

 deepens when the animal shrinks up, and the eye is concealed. Usually the 

 eyes cannot be distinguished in an external examination, but two specimens 

 I managed to get so well distended that the eyes were clearly visible. 

 Captain Hutton, in his brief account of the New Zealand Sifhonaridae, 

 says no eyes are present.* 



The eye is of the usual molluscan type — densely pigmented, and con- 

 taining the usual homogenous lens filling its cavity. 



Fig. 6. — Reproductory System ; x 2. 



^" 



(■(/, Common duct — glandular region ; cd' , common duct — non-glandular region ; hd, her- 

 maphrodite iluct ; lid' , small process formed of coil of hermaphrodite duct ; 

 hg, hermaphrodite gland ; lig' , point at which hermai)hrodite duct entei's the 

 common duct ; p, penis ; pro, prostate ; stlul, spermotheca duct ; sth, spermo- 

 theca ; -w, seminal vesicle ; f/p, genital pore. 



Beiyroductive System. Figs. 6, 7, and Plate XXIX, fig. 3. 



Siphonaria ohliquala is hermaphrodite ; the organs of reproduction are 

 both large and complicated, and comprise a hermaphrodite gland, a large 

 glandular common duct, spermotheca, and a large penis (fig. 6 ; hg, cd, 

 sth, p). These occupy a large part of the right half of the body-cavity. 

 The genital products arise in the hermaphrodite gland, a dull orange- 

 coloured organ lying partially imbedded in the digestive gland on the right 

 side, near the posterior end of the body. It consists of several lobes, and 

 on gently separating these then", can be seen issuing from them little white 

 ducts, which unite to form a main duct — the hermaphrodite duct. This 



* Trans. N.Z. Inst., vol. 15, p. 140. 



