210 J. GRAHAM KERR. 



chambers point towards the still later condition to be met with 

 in Sepia (D), where the septum has disappeared — a faint rudi- 

 ment remaining in the form of a transverse fold rising up from 

 the floor of the common chamber*. 



X. Summary of Conclusions. 



1. The perivisceral cavity in Nautilus is remarkable for the 

 almost equal participation in its formation of both coelom and 

 hsemocoel. 



2. The coelom consists of two distinct chambers — genital 

 and pericardial — separated by a perforated septum. 



3. Each of these coelomic chambers opens to the exterior 

 by a pair of nephridia. 



4. The genital ducts of the Cephalopoda represent portions 

 of nephridia. 



5. The ovary is remarkable for its extremely archaic 

 character — an ovigerous region of the coelomic epithelium, 

 roofed in by a simple upgrowth of the coelomic wall. 



6. The ova arise from syncytial masses of protoplasm. 



7. The testis is also archaic in character, and similar to the 

 ovary in its main features. Its cavity, however, has become 

 subdivided into numerous delicate tubes for the provision of 

 increased area of the spermatogenetic epithelium. 



8. The penis is a paired structure, its left moiety, however, 

 remaining rudimentary. 



9. An elaborate buccal nervous system is present. 



10. The "inner inferior lobe" is innervated not by a pair of 

 distinct ganglia, but by a continuous nerve-cord. 



11. Round the base of the postanal papilla is a curious 

 system of skin-glands. 



* The view advocated by Grobben (Morph. Stud. p. 39) that the condition in 

 Sepia is the more primitive, and that it represents a stage in the evolution of the 

 condition met with in the other Mollusca, seems to me untenable. 



