1896.] NATURAL SCIENCES OF PHILADELPHIA. 341 



we compare it with the simpler and very different digestive tract in 

 Prophysaon, Limax, or the Helices. 



The liver extends forward nearly as far as the anterior loop of the 

 intestine, and backward to the tail (PI. XIII, fig. 1), enveloping and 

 partly coucealing the convolutions of the intestine in all three genera. 



The suboral gland (PI. XIII, fig. 1) is about half as long as body, 

 and lies free, not imbedded in the muscles of the foot. 



GENITALIA. 



In Avion, Ariolimax and Aphallarion the genitalia lie quite dif- 

 ferently in the body-cavity from those organs in Limax or Prophysa- 

 on, the whole system being crowded forward. The albumen gland 

 (Pl.XIII, figs. 1 and 2) lies to the left of the anterior loop of the intes- 

 tine, almost entirely forward of the middle of the body-cavity. The 

 distal end of the albumen gland turns down the left side and extends 

 part way across the body beneath, often showing a longitudinal 

 impression made by the suboral gland. (This is seen at I. gr. in fig. 

 14 of Plate XIV.) At the base of the albumen gland the ovotestis is 

 closely packed (PL XIII, fig. 1) in Ariolimax and Aphallarion, and 

 its duct is largely imbedded in the albumen gland ; but in Arion the 

 ovi-sperm duct follows the course of the mid-gut backward, and the 

 ovotestis is situated at the tail, behind the stomach (PI. XIII, fig. 3). 



The penis in Ariolimax lies obliquely across the viscera, overlying 

 salivary glands and crop. It is seen removed from its natural posi- 

 tion in PI. XIII, fig. 1. 



In treating of Arion and allied forms, Dr. Simroth, the distinguished 

 German malacologist, has discriminated between a true penis and 

 that enlargement of the anterior end of the vas deferens seen in 

 Arion, etc., which he has termed the Patronenstrecke. 



The senior writer, in dealing with Helices, made the same distinc- 

 tion.^ The penis is an evertable sack, provided with a retractor 

 muscle. The "Patronenstrecke," or, as we have termed it, the epl- 

 phallus, is not evertable, and has no retractor muscle ; its function 

 being merely to gather the spermatozoa into packets or spermato- 

 phores ; and it is strictly homologous with the lower portion of the 

 vas deferens of ordinary snails. In the vast majority of snails in 

 which the vas deferens is modified into an epiphallus, it occurs in 

 connection with a normally developed penis, as in fig. 14, PI. XIV. 

 In Arion, Aphallarion, Prophysaon, and some other genera, the true 



2 Proc. Acad. Nat. Sci. Phila., 1892, p. 388. 



