ADDENDA TO MEMOIR I. 63 



On the Metamorphoses of the Crustacea. 



In I'iate VIII. fig. I, is given a representation of theZoe or 

 Larva of the common or edible Crab, (Cancer pagurus,) 

 alluded to page 9, and which should have accompanied the 

 Memoir it was intended to illustrate, had not the plates 

 been previously filled. Immediately beneath the magnified 

 figure, the animal is given of its natural size : on com- 

 paring these figures with those in Plate II, we shall gain 

 a tolerable idea of the disparity in size, between a Zoe 

 newly hatched and one which has attained its full develope- 

 ment, and of the changes which the various parts undergo 

 during the growth of the animal ; it must not be taken for 

 granted, nevertheless, that these are the Zoe of the same 

 species of Crab, for although the Zoes of different genera 

 resemble in the main, they yet appear to present variations 

 which may enable an acute observer to pronounce as to 

 the species, when we become more familiar with these 

 curious animals : the most obvious and remarkable diffe- 

 rence which the present figure exhibits, is the total absence 

 of the sub-abdominal fins, and the natatory division of the 

 two pair of feet, being provided with only four terminal 

 plumose setae. Zoes of this latter kind or in their 3'ounger 

 stages, are very numerous in the harbour of Cove during 

 Spring, while those of full growth are of comparatively 

 rare occurrence, so that it is probable that multitudes of 

 them fall a prey to the other inhabitants of the deep, 

 neither their grotesque figure, nor the extraordinary length 

 of their spines, affording a sufficient protection against 

 many of their enemies. 



Subsequent to the discovery announced in the first 

 Memoir, p. 8, viz. that Zoe in undergoing a metamorphosis, 

 appeared to pass into some form of the Decapoda, the 

 author became desirous of ascertaining whether it might 

 not be possible to hatch the ova of some of these animals, 

 so as to afford a satisfactory confirmation of so novel and 



