COTTHEI.L. — Aiuitomii of Sipliiiiiaiia ()hli(|uata. 593 



For staining pieces of the tissues to be mounted wliole 1 used alum 

 carmine ; for sections borax carmine and picro-carmine gave good results, 

 except in the case of the genital duet, whicli I found difficult to get well 

 stained : this organ requires three to four days' soaking in the stain. This 

 difficulty arises in all probabihty owing to its size. In some preparations 

 I used picro-nigrosine to show up the connective tissue, which it stains 

 l)hie. 



Affinities of Siphonaria obliquata. 



In the original tliesis I discussed at some length the affinities of >S'. ohli- 

 quata. Results arrived at may be summarized briefly as follows : — 



Opisthohranch Characters. 



1. The spermoviduct is undivided throughout its length, a condition 

 not characteristic of the Pulmonates. Some closely related genera, how- 

 ever — e.g., Gadinia and Aniphibola — have the duct divided. 



2. The condition of the hermaphrodite gland. 



3. The gill is possibly a modified ctenidium, but some authorities con- 

 sider it a secondary structure. 



Pu Imonote Characters. 



1. Large mantle-cavity, with small contractile respiratory pore. 



2. Presence of a lung by which aerial respiration may be effected. 



3. Presence of a pedal gland opening anteriorly between head and foot. 



4. Its mode of life differs from that of Opisthobranchs. 



In conclusion, I wish to acknowledge my indebtedness to Dr. Benham 

 for many valuable suggestions in preparing the present paper for publication. 



Bibliography. 



1. Bronn's " Thierreichs." pi. 77, figs, xv -xix (f866). 



2. Cooke : Cambridge Nat. Hist. — Mollusca. 



3. Haller : " Die Anatomic v. Siphonaria gigas, eines Opisthobranch. 

 Gasteropod" (Arbeit. Zool. Inst. Wien, x, f892). (Abstracted in Zonl. 

 Jahresbericht, f892.) 



4. Hutton: Trans. N.Z. Inst., vol. f5. p. 140 (1882). 



5. Kohler : " Beitrage z. Anatomic des Gattung Siphonaria " (Zool. 

 Jahrb., vii— Morph. Abth.). (Abstracted in Zool. Jahresbericht. 1893. p. 46.) 



6. Lankester : Article on Mollusca in Encycl. Brit. 



7. Lang : " Text-book of Comparative Anatomy," 2nd cd., pt. 2 — • 

 Mollusca. 



8. Pelseneer: Q.J.M.S., 37, n.s. (1895), p. 99. "Hermaphroditism in 

 Mollusca." 



9. Pelseneer : " Prosobranches aeriens et Pulmones' branchiferes " 

 (Arch. Biol., xiv, p. 351). (Abstracted in Zool. Jahresbericht, 1895, p. 29.) 



10. Pelseneer : Mem. Cour. Mem. Sav. Etrang. Acad. Bruxelles, vol. 53. 

 (Abstracted in Zool. Jahresbericht, 1894, p. 39.) 



11. Perrier : " Traite de Zoologie," 1897, p. 1967. 



12. Plate : Sitzber. Acad. Berhn, 1894, p. 217. (Absti-iicted in Zoo). 

 Jahresbericht, 1894, p. 52.) 



