456 REPORT ON ZOOLOGY, MDCCCXLIV. 



Gurlt (in these Archives, 1844, Bd. i, p. 322) lias ob- 

 served that the small varieties of Strongyhts armatus (six to 

 seven lines in length) which occur in the aneurismal mesen- 

 teric artery of the Horse are unarmed. These so-termed 

 varieties are only the young conditions of Strongylus 

 armatus ; the armature does not become visible till after 

 subsequent moultiugs. Gurlt observed the cephalic extre- 

 mity of these young Strongyli to be surrounded with a 

 membranous oral vesicle, from out of which the little oral 

 teeth already glistened. The caudal extremity, also, of the 

 male becomes changed in the process of growth, so that 

 these animals consequently undergo, as it were, a meta- 

 morphosis, which had been already noticed by Mehlis. The 

 circumstance that the bronchi of the Porpesse are always 

 crammed with such a great multitude of worms (Stronyylus 

 infiexus] is stated by Eschricht (Isis, 1843, p. 280) to be the 

 cause of this Cetacean possessing such a limited power of 

 diving. 



For a series of interesting researches on various nernatoid 

 worms, and especially with reference to their development, 

 we are indebted to Kolliker. (Miiller's Archiv, 1843, pp. 69 

 et scq.) In CucuUanus elegans he found no spermatic cells 

 (spermatozoida) in the female sexual organs. The ova of 

 this worm, which were situate somewhat deeper in the 

 uterus, all nevertheless presented the first indications of an 

 already commenced development. Kolliker was unable to 

 observe the very earliest stages in the formation of the 

 embryo. He observed first two large cells containing single 

 nuclei, which completely filled the cavity of the egg-mem- 

 brane. Further on he found ova, which contained three 

 nucleated cells, two smaller, and one larger, and which 

 might be regarded as embryonic cells. These nucleated 

 cells become less in size, and more numerous, by an endo- 

 genous formation of cells, up to the appearance of the ver- 

 miform body of the embryo, and at the same time the 

 ovum itself continues to increase. Previous to the forma- 

 tion of the worm, the mass of embryonic cells becomes 



