248 Analytical Notices of Books. 



anus, in which the intestine, now occupying the entire cavity of the pro- 

 cess terminates. At the same time the extremity of this caudal process 

 is gradually bent forwards beneath the central part of the embryo, until it 

 is brought nearly into contact with the labrum. The maxillae now begin 

 to shew themselves ; first, the three anterior pairs, nearly in contact with 

 each other, but at some little distance behind the mandibles ; and after- 

 wards the fourth and fifth pairs, the former arising from the spot where 

 the hinder part of the body is bent upon the fore part, the latter from the 

 portion which is bent upwards. In a short time, however, the posterior 

 maxillae are brought, by a change in the relative position of the parts, into 

 the same level with the anterior. As their growth proceeds, the latter 

 increase much more slowly than the former, so that at the close of this 

 period the fifth pair are four or five times as large as the first, and so on 

 in proportion with regard to the intermediate ones. Their extremities, 

 as in the antennae and mandibles, separate from the surface of the central 

 piece, and gradually become lobed, the two anterior pairs having each 

 two lobes, and the three posterior, three. A longitudinal sulcus and six 

 transverse ones, the latter corresponding with the several pieces of the 

 trophi, now become visible on the surface of the central piece. 



Very shortly after the appearance of the hindermost pair of maxillae, 

 the five pairs of true legs are produced in regular succession from before 

 backwards, on that portion of the tail-like appendage, which is turned 

 upwards. Each of these, in its early stage of developement, is exactly 

 similar to the hindermost maxillae. Soon afterwards there appears on the 

 outer side of the base of each, a small process, the rudiment of the 

 future branchiae. In their relative proportion, the legs increase inversely 

 with respect to the maxillae; the anterior being at the close of this period 

 about four times as long as the posterior. The true tail also now becomes 

 more clearly developed, and the rudiments of its foliaceous appendages 

 are visible at its extremity. At the same time six transverse furrows, 

 the indications of its future articulations, are seen on its under surface. 



The authour next proceeds to trace, with great minuteness, the forma- 

 tion of the internal organs, regarding the lamina of the embryo from 

 which the intestines are derived, and which lies in contact with the vitellus, 

 as mucous membrane, while he treats the outer lamina from which the 

 external organs take their origin, as serous membrane. First appear the 



