ORIGIN OP THE SEXUAL CELLS IN HTDROTDS. 6J7 



Recent Researches upon the Origin of the Sexual 

 Cells in Hydroids.^ A Review. 



By 

 A, G, Bourne, B.Sc, liond. 



The question as to the place of origin of the sexual products 

 of Hydroids is one upon which very various opinions have of 

 late years been current. The ectoderm and endoderm have, 

 in turn, been put forward as giving rise to either, or both, eggs 

 and spermatozoa. 



Kleinenberg, in speaking of Hydra, and F. E. Schultze, of 

 Cordylophora, state that both products are derived from the 

 ectoderm, a result with which Weissmann agrees. 



Grobben has observed the same origin in Podocoryne 

 came a, and F. E. Schultze in Sarsia tubulosa. The 

 Hertwigs have shown the same ectodermal origin of both 

 elements in numerous medusae; and lastly, Ciamician has 

 shown the same origin in Tubularians, Weissmann having 

 arrived at the same conclusions even before Ciamician's pub- 

 lications. 



On the other hand Weissmann has clearly demonstrated 

 both products to have an endodermic origin in Plumularia, 

 Sertularella, and Eudendrium. 



> Weissmann, A. " Observations sur les cellules Sexuelles des Hydroides." 

 'Bibliotheque de I'ecole des Hautes Etudes, Section des Sciences Naturelles,' 

 xxiv, No. 3. 



Varenne, a. De. " Sur I'origine des spermatozoides chez les Hydraires," 

 ' Comptes Readus,' xciii, pp. 1032 — 1034. " Developpement de I'oeuf de la 

 Podocoryne carnea," ' Comptos Rendus,' xciv, pp. 892 — 894. ' Recherches 

 sur les Polypes hydraires, (Reproduction et Developpement),' Paris, 1882, 

 Svo, (104 pp., 10 pis.). 



