124 



Dr. Strethill Wright's Observations on 



summit of the reproductive polyp of the latter, and which are 

 the last rudiments of tentacles. The polypidom consists of a 

 close network of flattened tubes, 

 from out of which the alimentary 

 and reproductive polyps spring 

 at distant intervals. The sperm- 

 sacs (one of which is shown in 

 the margin at fig. 1, attached 

 to the reproductive polyp) differ 

 from those of Hydractinia in 

 having the endoderm attached to 

 the ectoderm at their distal ex- 

 tremities, as I have figured else- 

 where (Edin. Phil. Mag. Jan. 

 1859) in the sperm-sac of Euden- Reproductive polyp of C. reticulata 

 drium rameum. This zoophyte with single sperm-sac : a, endo- 

 resembles the Sertulariada3 in derm; b, ectoderm; c, cavity con- 

 the simple columnar form of its taimn S spermatozoa, 

 non-tentacled reproductive polyps, and forms the connecting link 

 between these organs in the Tubulariadse and Sertulariada?. It 

 exhibits the most degraded form of the reproductive polyp, pre- 

 viously to the latter being altogether dispensed with and the 

 generative sacs being developed directly from the polypaiy. 

 Thus we have, in the chain of degradation, — 



Generative sacs or medusoids attached to ordinary ah- "1 Clava, Coryne, 

 mentary polyp, as in f &c. 



Generative sacs attached to reproductive alimentary po- "1 Podocoryna 

 lyp, which differs from ordinary alimentary polyp in \ fucicola 

 having fewer tentacles J (Sars). 



Generative sacs attached to reproductive polyp with rudi- \ Hydractinia 

 mentary mouth and tentacles, as in J echinata. 



Generative sacs attached to reproductive polyp without "I Eudendrium 

 mouth or tentacles ; summit of polyp surmounted by a V confertum 

 cluster of large thread-cells, as in J (Alder). 



Generative sacs or medusoids attached to reproductive po- "I Cionistes, 

 lyp without mouth, tentacles, or cluster of thread- > Sertularia, 

 cells, as in J Campanularia. 



Reproductive polyp divided longitudinally into several 1 Eudendrium 

 portions, each surmounted by its cluster of large thread- | arbusculum 

 cells; sperm-sacs formed, as in Hydra, by simple )■- (T. S.W.), 

 dilatation of the ectoderm; each division of polyp | E. capillarel 



transformed into a ' moniliform' sperm-sac, as in J (Alder). 



f Atractylis 



Generative sacs or medusoids attached to the polypary, 

 as in 



(T. S. W.), 

 Hydractinia 



(Alder and 



T. S. W.), 

 Cordylophora 



(All man). 



