ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 47 



anterior orifice. "When protruded, part of the wall of the sac is pro- 

 truded with it. The rostellum is provided with longitudinal and circular 

 muscles, and in the sac there is a circular musculature from which 

 numerous hundles of oblique or longitudinal fibres are given off. There 

 are from twenty-four to twenty-eight hooks on the rostellum. The 

 suckers can elongate like arms, and each is capable of independent 

 movement. They and the rostellum may break off mechanically from 

 the scolex, without the latter suffering any apparent injury. The neck 

 may vary in length. The proglottids differ remarkably in form and 

 number ; one very important characteristic is that their hinder angles 

 project in the form of more or less regular triangular points. The 

 separate joints have a certain power of shutting in upon one another. 



By the examination of well-preserved eggs the authors have been 

 able to see that the substance in the space between the two egg-membranes 

 is often homogeneous near the inner membrane, and that the latter has 

 two scarcely evident swellings, one of which corresponds to the pole of 

 the egg, while the other is just by the other pole. In certain cases it is 

 easy to see that the coiled filaments in the substance correspond to the 

 two swellings. The longest axis of the egg is from 43-53 fj. long, tho 

 shortest from 35-40 ju. 



Tsenia marina from the mouse is probably a mere variety of T. nana, 

 differing chiefly in its greater length, and in the ordinarily greater size 

 of the just mentioned swellings. 



Fourteen new cases of T. nana have been observed, chiefly in children : 

 and it may be said that T. nana is much more common than other human 

 cestodes in Sicily. To discover it, it is not sufficient to examine freces 

 once only. The number present varies from forty or fifty to four or 

 five thousand ; the hosts frequently suffer little or no pain, but this, of 

 course, is not always the case. Filix mas is an appropriate remedy. 



Sphyranura osleri.* — Prof. E. Eamsay Wright and Mr. A. B. 

 Macallum give a detailed account of this ectoparasitic Trematode, 

 which is intermediate between Gyrodactylus and Polystomum, and may, if 

 some slight alteration be made in the diagnosis, be placed in the sub- 

 family Polystomida3, as defined by Taschenberg. Sphyranura is found 

 on the skin of Menobranchs, where it is very obvious on account of its 

 want of colour. 



The investing membrane is very elastic and is provided with a very 

 large number of conical bodies, which the authors regard as tactile 

 organs ; the deep surface of the membrane does not lie on the circular 

 muscles, but is separated from them by a narrow space containing fluid ; 

 the presence of tactile organs may be correlated with the comparatively 

 active life led by this parasite, and as compensatory for the absence of 

 eyes. The worm holds on to its host with great pertinacity, owing to 

 the possession of hooks and suckers on the ventral surface of the character- 

 istic caudal lamina. The most striking point about the musculature is 

 the fact that the diagonal fibres, which are so abundantly present in the 

 larger Distomes, are hardly represented. With regard to the minute 

 structure of the muscles, as to which various students of Trematodes 

 have given different accounts, the authors tell us that the longi- 

 tudinal caudal bands, which are generally over 2 mm. in length, offer 

 favourable material for the study of individual fibres. They find, that 



* Journ. of Morphology, i. (18S7) pp. 1-48 (1 pi.). 



