176 METAMOEPHOSES OF MAN 



stance of extreme variety in the phenomena ex- 

 hibited. 



In the case of the lower forms of animal life, Nature 

 seems, as it were,- to despise that uniformity in 

 embryogenic laws which is so characteristic of the 

 development of the higher groups. We find the 

 most decided differences between the developmental 

 processes of even species of the same genus. Thus, 

 according to Lowen, the medusoid proglottis of one 

 campanularia remains attached to the polyp which 

 gave it birth ; whilst it is stated, on the authority of 

 M. Desors, that in another species — the gelatinous 

 Campanularia — it bursts the reproductive capsule on 

 arriving at the same condition, and swims about 

 freely, undergoing its metamorphosis in the sur- 

 rounding water.* It was also observed by the same 

 naturalist, that some of the polypary's branches pro- 

 duced only male, and others only female, repro- 

 ductive bodies. In fact, the greater the advance made 

 in the field of discovery, the larger the field appeared 

 to be, and the greater the number of new points 

 of view which it presented. We shall now endea- 



* " Lettre sur la Generation Medusipare des Polypes hydraires." 

 — Annales des Sciences naturelles, 1849. I am sorry that I cannot 

 quote some of the passages from this memoir, especially those 

 regarding the difference between the author's observations and 

 those of Saars on the development of Aurelia. Desors saw the 

 proglottis (the fully-formed Medusa) produced by gemmation from 

 the interior of Scyphistoma (the Medusa in the hydroid state), and 

 lifted up in piled form, from the mouth of the polyp, which 

 remained, after entire separation of the proglottides. As the 

 matter is one dependent on plain observation, it seems to me that 

 both naturalists may be right, and that these differences may be 

 adequately explained by supposing a difference of species. 



