1 



INTRODUCTION. 



tures were observed swimming about as before. To 

 render the matter, if possible, still more certain, some 

 of the ova were opened, and the embryos extracted; but 

 shortly afterwards I had the pleasure of witnessing, be- 

 neath the microscope, the natural bursting and escape 

 of one precisely similar in form to those found so abun- 

 Fig- c. dantly in the water. Thus, 



then, there is no doubt 

 that these grotesque- 

 "^ ^/z /-JM] "('sm looking creatures are the 



young of the Carcinus 

 Mcenas ; but how diffe- 

 rent they are from the 

 adult need hardly be 

 pointed out any further 

 than by referring to the 

 fig. {c). When they first 

 escape they rarely exceed 

 half a line in length. The 

 body is ovoid, the dorsal shield large and inflated, on its 

 upper edge and about the middle is a long spine, curved 

 posteriorly and rather longer than the diameter of the 

 body, though it varies in length in different specimens ; 

 it is hollow, and the blood may be seen circulating- 

 through it. The upper portion of the body is sap- 

 green, and the lower semi-transparent. The eyes are 

 large, sessile, and situated in front, and the circum- 

 ference of the pupil marked with radiating lines. The 

 lower margin of the shield is waved, and at its posterior 

 and lateral margin, is a pair of natatory feet. The tail 

 is extended, longer than the diameter of the shield, 

 and is composed of five equal annulations, beside the 



