171 



similar, and are beginning to show evidences of a 

 biramose structure. The first and second pairs of niaxilli- 

 pedes are large and biramose. The protopodite is large. 

 The endopodite and exopodite have few setae. Towards 

 the end of the protozoea stage the cuticular covering 

 becomes very loose, and beneath can be seen the 

 developing organs of the first zoea stage. Chromato- 

 phores are present at the sides of the body. 



First zoea (PI. XIII, figs. 85, 80, 87). This stage 

 is generally seen about three or four hours after hatching, 

 and probably lasts for at least ten days. The important 

 difference between this and the previous stage is the 

 presence of the large frontal and dorsal spines. The 

 latter is about half as long as the body, and the frontal 

 spine is about two-thirds the length of the body. Both 

 are tipped with a red pigment. The lateral spines are well 

 developed. The branched chromatophores are well 

 developed. The number of appendages appears to be the 

 same as in the previous stage, but they are more highly 

 developed. Each antennule bears a group of setae 

 at its tip. The antennae and both pairs of 

 maxillae are biramose. The exopodites of the maxilli- 

 pedes each bear four long setae. the third maxillipedes 

 and the pereiopods and the associated gills are present as 

 extremely small buds, which are hidden beneath the 

 cephalothoracic shield. The pleopods may be seen for the 

 first time as extremely small tubercles. In some examples 

 of both the protozoea and the first zoea there was a pair of 

 tubercles present on the second abdominal somite. The 

 telson differs from that of the previous stage in having 

 two extremely long posterior branches. 



Zoea stages II, III and IY. I have not been able to 

 identify these stages in Cancer pagurus, but in Carcinus 

 maenas they have the following essential characters. They 



