Miscellaneous. 75 



On a new Form of Vesicular Worm with Exogenous Budding. 

 By M. A. ViLLOT. 



The curious larva of a Tseniid, which I now propose to make known 

 under the name of Urocystis prolifera*, is, like the Staphylocystest, a 

 parasite of Glomeris limbatus ; but it presents the peculiarity that it 

 lives in the same host in various degrees of development — namely, in 

 the vesicular state properly so called, free iu the visceral cavity, and 

 in the state of scolex, encysted in the adipose body. 



Urocystis prolifera, in the vesicular state properly so called, pre- 

 sents for our consideration three very distinct parts — a head, a body, 

 and a caudal vesicle. These three parts, which are in perfect con- 

 tinuity of tissue, are invaginated one within the other, the head in 

 the body, and the body in the caudal vesicle. 



The head is oval, more or less inflated laterallj', truncate in front, 

 and narrowed behind. It bears four sucking-disks and a very long 

 rostellum. The latter deserves to be described in detail. It is 

 invaginated in the head by its posterior extremity, and upon itself 

 by its anterior extremity. Erom this it results that the head of the 

 worm terminates by a sort of funnel of invagination, having perfectly 

 the aspect of a frontal sucking-cup. The inner Avail of this infun- 

 dibulum presents numerous transverse folds, formed by the contrac- 

 tion of the elastic fibres of which it consists, and is armed w^th a 

 circlet of hooks so small that it is impossible to count them. These 

 hooks are packed very closely together ; and to distingiiish them it is 

 necessary to employ a magnifying-power of 600-900 diameters ; with 

 lower powers we only see a chitinous ring of a brilliant yellow colour. 



The body {recejJtaculum cajyitis) is united by the neck to the pos- 

 terior part of the head. It is formed by a very delicate membrane, 

 so closely pressed against the inner wall of the caudal vesicle that it 

 is difficult to distinguish it therefrom. We only remark beneath 

 the neck a sort of pad, formed of embryonic cells, like the paren- 

 chyma of the head. The peduncle which unites the body to the 

 caudal vesicle can only be detected with difficult}^, in consequence 

 of the transparency and contractility of the tissues and the narrow- 

 ness of the orifice of invagination. 



The caudal vesicle is oval, slightly acuminate in front, obtuse 

 posteriorly. It is formed, as usual, of anatomical elements of two 

 kinds — an outer layer of interlaced elastic fibres, and an inner layer of 

 connective tissue. Its contractility, which is very marked, enables 

 the animal to move in all directions. The scolex occupies only two 

 thirds of its cavity ; and there is in the posterior region a very con- 

 siderable vacancy. 



The dimensions of the different parts of the worm are as follows: — 

 hooks 0-001 millim. ; diameter of the trunk in the invaginated state 

 0-03 ; diameter of the sucking-disks 0-02 ; length of the scolex in 

 the invaginated state 0-07 ; length of the caudal vesicle 0*09 ; breadth 



* Incorrectly called Urocystis prolifer by M. Villot. 

 t See ' Annals,' ser. 5, vol. i. p. 258. 



