142 Scientific Intelligence. 



The basicerite, in the embryo Decapod, is far from being the trifling 

 joint seen at the base of the scale-like appendage ; but is, in fact, that 

 large supporting joint which is the first to make its appearance, and 

 which often reaches, with its exocerite, a large size before any trace of 

 other joints, either coxal or terminal, can be perceived. In the figures 

 accompanying the valuable observations of Dr. C. Spence Bate {Phil. 

 Trans., 1858, pi. xl, f. B. 3, etc.), this character of the basicerite is well 

 shown in representations of the Zoea of Carcinus mcencts. Here we 

 have the joint in question very large, armed with a long spine on one 

 side and the exocerite on the other, while the rest of the antenna is in 

 a rudimentary condition, and there is no coxocerite visible. This latter 

 joint, with its areola, makes its appearance at a later date, at the base of 

 the basicerite. 



The large comparative size of the exocerite in the embryo, is in ac- 

 cordance with what we observe in the gradations of adult Crustacea. 

 Those lowest in the series have generally the external branch of their 

 members most developed ; as we rise in the scale, we observe the inner 

 branch becoming more and more developed, while the outer branch is 

 reduced and may disappear entirely. Compare, for example, the thoracic 

 feet of some Schizopods with those of the Caridea and Brachyura. 



