128 



LIFE, IN ITS LOWER FORMS. 



kingdom stand to higher animals, and minister less to the 

 perpetuation of their own species than to the sustenance 

 of man." * 



The researches of MM. Ercolani and Ve]la,t on the em- 

 bryogeny and development of the Nematoid (thread-like) 

 Intestinal W orms, have revealed some details which, though 

 not so startling as those discovered by Dr Von Siebold on 

 the Teenioids, possess considerable interest. 



"The Thread Worms do not undergo a true metamor- 

 phosis ; the changes observable in the embryo are only 

 phases of developments ; but as in the Teenioids the gene- 

 rative organs are the last formed, and are not perfect till 

 the complete development of the animal. 



" The cessation of movement and the fluidity of the 

 body in the Nematoids are not sufficient signs of the death 

 of these animals, as they recover from this state as soon 

 as they are placed in warm water ; even in the state of 

 embryos, although completely dried up, they return to life 

 very quickly by this means. The Nematoid w T orms con- 

 sequently die with great difficulty ; the ova and embryos 

 are endowed with a marvellous tenacity of life ; they even 

 exhibit signs of life after immersion for six days in alcohol 

 of 30 degrees. 



" This tenacity of life, joined with the power of develop- 

 ment of the ovum when placed in circumstances different 

 from those in which it lives naturally, besides giving evi- 

 dence of new and important facts, destroys the strongest 

 arguments employed by many naturalists in favour of 

 heterogeny. J 



* Comp. Anat. ; i. 76. (Edit, i.) 

 t Comptes Rendus, 24th April 1854. 



% Heterogeny, a total difference of form between parent and offspring. 



