THE COASTS OF SICILY. 273 



who have shown that in the Rays there are certain 

 portions of the body in which the blood-vessels cease 

 all at once, and where the blood flows freely into 

 cavities, whose arrangement recalls to mind that 

 which exists in some of the lowest animals. M. 

 Robin in following his first researches, has extended 

 these results to several species of the family of the 

 Squalidae. We are convinced that the question will 

 not remain where it now is, and that in the course of 

 a few years we shall undoubtedly meet with facts in 

 the highest Mammals, and even in man himself, 

 which, if not entirely similar, are at least almost 

 analogous. The results at which MM. Dujardin 

 and Natalis Guillot have arrived by the study of 

 the minute structure of the liver, appear to offer a 

 certain guarantee of the success which will attend 

 the investigations undertaken in this direction. 



The circulation, therefore, which is at first entirely 

 lacunary, is consequently reduced to a sort of vague 

 agitation, which, as it gradually becomes regulated, 

 assumes a more and more vascular character, in 

 proportion as we rise higher in the animal scale. 

 This is the general fact or tendency which pre- 

 dominates in the progressive development of the 

 circulatory apparatus. 



The same tendency is to be met with in organisms 

 in the act of formation, whether we examine the 

 development of a normal germ, or whether we study 

 the manner in which certain accidental tissues are 

 constituted. The area vasculosa, in which the 

 embryo of the bird seems to draw the first elements 

 necessary to its evolution, presents at first nothing 



VOL. I. T 



