( 53 ) 

 SESSION 1860-61. 



FRIDAY, DECEMBER 7, 1860. 

 "William Andrews, M. E. I. A., President, in the Chair. 

 The previous Minutes were read and signed. 

 Henry Lawson, M.D., read the following paper: — 



ON THE GENERATIVE SYSTEM OF HELIX ASPERSA AND HORTENSIS. 

 (with a PLATE.) 



The following observations upon the reproductive system of Helix as- 

 persa, our commonest Irish snail, are given as the result of a series of 

 dissections and microscopic examinations, made during the past summer. 

 The object of the paper is twofold — firstly, to supply a deficiency in our 

 text-books on zoology and comparative physiology, by publishing the 

 descriptive anatomy of the species of Helix most widely distributed in 

 Ireland, and of thus affording to the student of natural history an 

 opportunity of verifying by dissection the descriptions given — a circum- 

 stance too much neglected by writers upon the subject, who prefer the 

 less difficult task of quoting, wholesale, the investigations of Cuvier, 

 which were made upon that species {Helix pomatid) most abundant in 

 his own neighbourhood. Secondly, to put forward my own opinion 

 concerning the relations of function of the parts which compose this 

 system. 



The generative organs of this animal are hermaphrodite in their 

 nature, and excessively complicated in their arrangement. They occupy 

 a larger volume of the body comparatively with the other systems than 

 at first one would be inclined to suppose, extending from one extremity 

 to the other, and seeming more or less closely related to every organ in 

 the economy of the creature. They present an external aperture ad- 

 jacent to the right upper tentacle, and terminate at the ovary, in the 

 final spire of the shell. For convenience, they may be divided into four 

 groups : — 



1. Female. 



2. Male. 



3. Androgynous. 



4. Appendicular. 



Of these, the female organs form by far the largest portion, and 

 extend over the greatest surface. They consist of an ovary, oviduct, 

 albumen-gland, and uterus. The ovary is a small, rather compact, fan- 

 shaped gland, spread over the last lobe of the liver, and, with it, included 

 in the terminal volution of the shell ; its broad, or basal extremity, is 

 most external, the narrow portion being directed inwards, to terminate 

 in the commencement of the oviduct. When separated from its attach- 



