Reviews and Notices of BooTcs. 63 



the present volume, in a very full and satisfactory manner. As 

 an example of a description interesting to every reader who takes 

 pleasure in contemplating the " creeping things innumerable " 

 that God has made in the sea, we quote the following description 

 of the habits of the Pleurohrachia rhododactyla, a little ball of 

 living jelly very common on our coasts in summer, and about the 

 size of a large pea. 



" The Ctenophorre differ essentially from the Discophorse. Both their 

 form and organs of locomotion give them a different appearance. The 

 Discophorse, setting aside the various modifications arising from marked 

 peculiarities of their outline, move like an umbrella, which, by alter- 

 nately opening and shutting, would make its way under water by means 

 of such movements. It is by the contraction of the body alone, or 

 rather by the agency of the motory cells which form the mass, that 

 motion is produced in these animals. Not so in the Beroid Medusae, 

 where, besides the action of the motory cells, the whole body, more or 

 less spherical or ovate, compact or split at one end, is kept swimming 

 by the flapping of innumerable small paddles arranged in vertical rows, 

 like the ribs of an orange, upon the outer surface. These rows are 

 generally eight in number, extending from one pole of their spheroid 

 body to the opposite, like the meridians of an artificial globe. But, 

 owing to the inequalities in the motions of their vertical flappers, and 

 their radiated arrangement upon the more or less spherical body, these 

 animals have a somewhat rotatory motion, unless the paddles move on 

 all sides with perfect steadiness and uniformity. 



' There can be scarcely anything more beautiful to behold than such 

 a living transparent sphere sailing through the water, coursing one way 

 or another, now slowly revolving upon itself, then assuming a straight 

 course, or retrograding, advancing or moving sideways, in all directions 

 with equal precision and rapidity; then stopping to pause, and remaining 

 for a time almost immovable, a slight waving of some of its vibrating 

 organs easily counterbalancing the difference of its specific gravity and 

 that of the water in which it lives. So Pleurohrachia may appear at 

 times, and so does it also appear when moving in a state of contraction. 

 But generally, when active, it hangs out a pair of most remarkable 

 appendages, the structure and length and contractility of which are 

 equally surprising, and exceed in wonderful adaptation all I have ever 

 known among animal structures. Two apparently simple^ irregular, 

 and unequal threads hang out from opposite sides of the sphere. Pre- 

 sently these appendages may elongate, and equal in length the diameter 

 of the sphere, or surpass it, and increase to two, three, five, ten, and 

 twenty times the diameter of the body, and more and more ; so much so 

 that it would seem as if these threads had the power of endless exten- 

 sion and development. But as they lengthen they appear more compli- 

 cated : from one of their sides other delicate threads shoot out like 

 fringes, forming a row of beards like those of the most elegant ostrich 



