NATURAL SCIENCES OF PHILADELPHIA. 



345 



Tcn-ac/ffr 



epi. 



1896.] 



inner body, which extends to the external orifice, where it terminates 

 in a penis-papilla (fig. 9, P. papilla). This internal body consists 



of a fleshy cylindrical tube (fig. 9, epi.) en- 

 veloped by a very thin-walled and minutely 

 corrugated outer tube (fig. 9, sheath of epi.). 

 This structure we can only interpret as an 

 introverted epiphallus, which has extended 

 entirely to the proximal opening of the penis, 

 carrying the penis-papilla at its summit. 

 This will be more clearly seen in the annexed 

 diagram. The clearer, because less ad- 

 vanced, penial morphology of ^. Californicus 

 bears out this view of the structure in A. 

 Colmnbianus, which is, moreover, more read- 

 Diagram of thepenisof i'j ^een in our preparations than in the flat 

 V. d. vas def- figures, necessarily complicated by lines to 

 show the ducts and layers of tissue not 

 visible from the outside' 



The female side shows a rather long vagi- 

 na, provided with a broad, split retractor 

 Spermatheca situated high, on a short duct. 

 Other organs call for no special remark. 



A. Columbiamis is a dimorphic species in most, perhaps all, local- 

 ities. There is a unicolored form, and one more or less heavily 

 spotted or blotched with black. This maculated form has received 

 the name "for7na maculatus " Ckll. It is in no sense a true variety 

 or subspecies but merely a " form," comparable to the glaucus form 

 of the dimorphic Papilio turtucs. 



Cockerell's "forma niger " was described from one specimen in 

 which the black blotches had coalesced, upper surface entirely blacky 



^ A similar penial structure has very recently been described and figured by 

 Charles Medley in the epiphallogonous genus Xanthomdon of the Helicidse. 

 In A", fodinalis Tate and A'. Adcockiana Bednall, a tube occupies the penis 

 cavity. ''This," writes Hedley, "I interpret with some hesitation as an in- 

 vaginated epiphallus, of which the distal end has grown to the atrium wall, 

 and which has drawn after it into the penis sac both vas deferens and the 

 retractor" (see Medley's anatomical appendix to Professor Ralph Tate's 

 report on the Mollusca of the Horn Expedition to Central Australia). 



No such structure has been described before ; and we are disposed to accept 

 Medley's ingenious interpretation of the morphologic problem. In Xantho- 

 melon the invaginated epiphallus is attached at the proximal end of penis sac. 

 This is not the case with Ariolbnax, in which the invaginated structure is to 

 that extent clearer. 



vv- 



Ariolimax 

 erens ; fpi. invaginated 

 epiphallus ; /• /. perfo- 

 rated penis papilla, ele- 

 vated on the epiphallus ; 

 0. extei-nal opening of pe- 

 nis. 



muscle, inserted high. 



28 



