1898.] NATURAL SCIENCES OF PHILADELPHIA. 257 



To dissect slugs use a small pan, say 4x6x1* inches, with a layer 

 of blackened wax on the bottom. Only a pair of fine scissors, a 

 pair of fine-pointed tweezers, a small scalpel and a supply of fine 

 pins, with, of course, the small lens usually carried by naturalists, is 

 necessary. Cut the outer integument across the head and along the 

 left side, pin sole down in the pan, with water enough to cover, open 

 by turning the dorsal integument to the right, and cut the rectum 

 where it enters the back. The digestive tract may then be studied 

 by picking awa} 7 the liver, and, with ordinary care, the genitalia 

 may be removed and isolated by cutting out a small area around 

 the genital orifice. After observing its insertion, the penis retractor 

 may be cut. 



If specimens are abundant, use another for the examination of the 

 muscles and pal Hal organs. Open by cutting just above the foot 

 groove all around the body; remove the sole, pin back downward 

 in the dissecting pan and remove the digestive and genital systems, 

 care being taken to break no muscles. The whole retractor system 

 will then be seen, and after study the muscles may be cut and the 

 diaphragm carefully removed, disclosing the kidney, heart and 

 lung, as seen in the figures on Plate XV. 



Use a large slug to begin with, such as Limaxmaximns, the Ario- 

 limaces or Aphallarion, and no difficulty not readily overcome will 

 be encountered. 



BIBLIOGRAPHY. 



Eeferences cited under the several genera and species comprise all or nearly 

 all writings upon American Arionidce. A catalogue of the foreign papers con- 

 sulted in our studies would unnecessarily extend this article, as the literature 

 is given almost in full in one or other of the following papers, which we have 

 found of especial use. 



Godwin- Austen, H. H. Land and Freshwater Mollusca of India, Pt. I, 

 pp. 46-65 (1882). 



Simroth, H. Yersuch einer Naturgeschichte der deutschen Nacht- 

 schnecken und ihrer europiiischen Yerwandten. Zeitschr. f. wissensch. 

 Zool., 1885, pp. 203-366. Bibliography on pp. 359-361. 



Simroth, H. Beitriige zur Kenntniss der Nachtschnecken. Nova Acta k. 

 Leop.-Carol. deutschen Akad. Wissensch., LIY, No. 1, pp. 1-91 (1889). 



Scharff, R. F. The slugs of Ireland. Sci. Trans. Boy. Dublin Society, 

 IV, Ser. 2, pp. 513-562. Bibliography, pp. 557, 558 (1891). 



Simroth, H. Die Nachtschnecken der portugesisch-azorischen Fauna. 

 Nova Acta, etc., LVI, pp. 201-424 (1891). Bibliography on pp. 416-419. 



Cockerkll, T. D. A. Check-List of Slugs. The Conchologist II, p. 158. 



Collinge, W. E. On some European Slugs of the Genus Arion. Proc 

 Zool. Soc. London, 1897, p. 439. 



