THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 

 No. 93. SEPTEMBER 1875. 



XX. — On the Primary Origin of the Sexual Products. 

 By M. Hermann Fol*. 



A MEMOIR of great importance from the point of view of 

 embryogenic morphology appeared at the end of last yearf. 

 This memoir is the fruit of the investigations made by E. van 

 Beneden on the mode of formation of the testis and ovary in 

 Ply dr actinia echinata and Clava squamata. 



The Hydractinia is particularly well adapted for this in- 

 vestigation, because its colonies are male or female ; each 

 colony contains individuals in different stages of development, 

 the sex of which is thus known beforehand. To this we must 

 add the simplicity of organization of the Coelenterata, especially 

 the Hydroida, which consist during the whole of their life 

 principally of the two primitive lamellse, the ectoderm and 

 entoderm — the mesoderm, represented by muscular fibres and 

 connective tissue, being very little developed. The results of 

 researches made upon an object so favourable must have an 

 almost absolute certainty, and deserve our full confidence. 



Van Beneden saw the testis form at the expense of a mass 



* Translated by W. S. Dallas, F.L.S., from the ' Bibliotheque Uni- 

 verselle, Archives des Sciences Physiques et Naturelles,' June 15, 1875, 

 pp. 104-111. 



t E. van Beneden, "De la distinction originelle du testicule et de 

 l'ovaire ; caractere sexuel des deux feuillets primordiaux de l'einbryon ; 

 hevmaphrodisme morphologique de toute individuality animale &c," 

 Bull. Acad. Roy. de Belgique, 3 e ser. tome xxxvii. 1874. 



Ann. & Mag. N. Hist. Ser. 4. Vol. xvi. 12 



