17 



cm, ray own observations do not, as yet, allow me to express a posi- 

 tive opinion where so much difference exists among observers. But 

 I am inclined to say that there is but one row of teeth in the crown. 

 For the same reason, that I have not observed the animal in the deve- 

 loped state sufficiently, I can say nothing about the four suctorial 

 disks described by all writers on the subject, and which, at all events, 

 are not visible in the animal when the head is retracted. And M. Livois' 

 supposition, that suckers like this must always be present in Entozoa, 

 with hooks at the cephalic extremity, is obviously unsupported by 

 Nature, for the whole class of Echinorhynchi have no suckers what- 

 ever, and yet find no difficulty apparently in infixing their heads into 

 the mucous membrane of the intestines. 



The body of the Echinococcus is covered with a thick, transparent 

 membrane, the inner surface of which is rough, the outer smooth, and 

 there appears to be a very narrow space between the inner surface of 

 the tunic and the central granular matter. It is in this space, or be- 

 tween the outer tunic and the central granular matter, that the pecu- 

 liar and curious transparent oviform bodies are placed, and only in 

 this situation, and they are not, as most suppose, disseminated 

 throughout the parenchyma of the animal. 



This disposition of the transparent oviform bodies may be ascer- 

 tained by inspection, having care to focus the glass slowly, and also 

 by observing their annular arrangement on the lateral margins of the 

 body, where the space in which they are situated is, as it were, seen 

 in profile. 



This position of them may also be proved by a simple experiment. 

 If a drop or two of acetic acid be added to the Echinococci in a glass, 

 the outer tunic will be seen immediately to swell or bulge out irregu- 

 larly, and finally to burst and disappear, being, in fact, dissolved, and 

 together with this, the transparent bodies escape, and also quickly 

 disappear, leaving the body of the animal but little diminished in size 

 or much altered in form, and without a trace of the oviform bodies, 

 or spaces where they could have been. The same change also occurs 

 as a consequence of decomposition, and in preparations that have been 

 long kept or ill kept, this deprivation of the external tunic and subja- 

 cent oviform bodies, gives the animal an appearance altogether diffe- 

 rent from its true one, although some of the published figures appear 

 to have been drawn from such altered specimens. 



The same considerations and the same simple experiment prove 

 that the body of the animal is composed internally of a tolerably solid 

 material, and is not simply a vesicle containing fluid, as it is usually 



TRANS. MIC. SOC. VOL. II. C 



