Miscellaneous . 157 



only phases of development ; thus the generative organs are always 

 the last formed, and are not perfectly presented until the complete 

 deyelopment of the animal. 



4. "The horny appendages and hooks, which are wanting in the 

 Cysticercus cuniculi in the first stages of its development, are also 

 wanting round the mouth of the Stronyylus armatus until after com- 

 plete development, and are then formed but slowly. 



5. " The eggs of the Ascaris meyalocephala of the horse may be 

 artificially developed in the pulmonary tissues of the dog. 



6. "The cessation of movement and the fluidity of the body 

 in the Nematoids are not sufficient signs of the death of these ani- 

 mals, 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 

 worms consequently 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. 



7. " This tenacity of life, joined with the power of development of 

 the ovum when placed in circumstances different from those in which 

 it lives naturally, besides giving evidence of new and important facts, 

 destroys the strongest arguments employed by many naturalists in 

 favour of heterogeny. 



8. " The ova of the Nematoid worms require a considerable time 

 for their development after being introduced with the food into the 

 bodies of animals ; they adhere at first around the villosities of the 

 mucous membrane of the intestine, whence they afterwards penetrate 

 to the peritoneum, there to complete their development free from all 

 danger of being eliminated, returning afterwards into the cavity of 

 the intestine. 



9. " This simple mechanism, in harmony with the laws which 

 govern the introduction of foreign bodies into the organism, may be 

 readily observed by examining the yellowish spots which occur in the 

 intestines of the rabbit, or in the caecum of the horse, which are 

 nothing but the ova of the Oxyuris of the rabbit or of the Stronyylus 

 of the horse ; amongst these ova we often meet with the microscopic 

 embryos of these Nematoids. 



10. " In the adult females of the Ascaris meyalocephala and lum- 

 bricoides it may readily be shown that the ova are not formed in the 

 last portion of the oviduct, but in the superior, slender portion which 

 represents a true ovary. 



11. " From the inner surface of the ovaries of the Ascarides just 

 mentioned, an immense quantity of elongated, pyriform bodies are 

 suspended ; these represent the Graafian vesicles of the superior 

 animals. 



12. " The Graafian vesicle, as in the higher animals, is not torn to 

 permit the passage of the ovum, but detaches itself completely from 

 the stroma, and loses its pyriform shape to become round, whilst the 

 membrane of the vesicle becomes the chorion of the egg. 



12. "The vitelline membrane is formed after the detachment of 

 the ovum." — Comptes Rendus, 24th April 1854, p. 779. 



