1 



INTRODUCTION. 



tares were observed swimming about as before, 

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

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

 shortly afterwards T 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- 

 Fl 'g- c - dantly in the water. Thus, 



then, there is no doubt 

 that these grotesque- 

 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 aline 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 



