ARION ATER. 



169 



The CEPHALIC RETRACTORS arise from three dis- 

 tinct and separate points, as is- usual in the genus ; 

 the PHARYNGEAL niuscle originating most posteri- 

 orly nearly in the median line behind the lung 

 cavity, and bifurcating about half-way for attach- 

 ment to each side of the buccal bulb ; the tenta- 

 cular retractors are broad and fiat, the left arising 

 from the hinder left-side of the lung periphery ; the 

 right retractor is somewhat similarly placed, but a 

 trifle removed from the lung ; both divide about the 

 middle of their course into a chief muscle for the 

 ommatophore of their respective sides of the body, 

 and a subsidiary one for the lower tentacle, the 

 latter branching again to send a slip to the buccal 

 or labial lobe. 



The reproductive organs are comparatively simple; the dark-brown spherical 

 OVOTESTIS is placed behind the stomach, and is traversed medially by an artery • 

 the HERMAPHRODITE DUCT IS long and tortuous, terminating in a slightly swollen 

 and acutely bent junction with the ovispennatoduct, representing the VESICULA 

 SEMINALIS ; the pale albumen gland is large and compact, but mucli indented ; 

 the OVISPERMATODUCT is very long ; the OVJDUCT is a delicate bluish ruffle above. 



Fig. 191. — Cephalic retractors of 

 Arion ater X 2. 



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Fig. 192. Fig. 193. Fig. 195. Fig. 196. 



The Reproductive system of adult and juvenile Arion aterCL.), showing the muscular arrangements 



and the modifications of the organs arising during growth X 3. 



Fig. 192. — The proximal end of the organs with the epiphallus removed to show the arrangement 

 of the retractor and attachment of the spermatheca. 



Fig. 193. — The organs as seen from the opposite side, with oviduct and genital retractor removed. 



Fig. 191. — Spermatheca and oviduct, showing attachment of retractor. 



Fig. 195. — Proximal end of sexual organs, showing their complex natural arrangement. 



Fig. 196. — Sexual organs of an immature example. 



alb.gl. albumen gland ; l.at. glandular lower atrium ; u.at\ and at, upper atrium ; ot. ovotestis ; 

 ov. oviduct ; osd. ovispermduct : ep. epiphallus, cut short ; sp. spermatheca ; v.d. vas deferens ; 

 r. genital retractor, showing attachment to spermatheca duct, oviduct, and atrium. 



naiTOwing below, wliile the yellowi-sh sperm-duct, or prostate, increases in calibre 

 as it descends ; the two channels being closely connected together ; the slender VAS- 

 DEFERENS expands into a thick EPIPHALLUS, which secretes the moderately slim, 

 brownish, and denticnlate spermatophore ; the ovately-globose SPERMATHECA is 

 connected by a shortiah stalk with the atrium, into which the epiphallus, oviduct, 

 and spermatlieca all debouch; the upper atrium, or "egg-sac,"is immensely bulged 

 at one side, the protuberance originating at the base of the ovidnct, and contains 

 an erectile lingiiiform appendage, which is probahl}'" a sarcobelum. The genital 



