INTRODUCTION. 



Ivii 



But one of the most remarkable peculiarities of this 

 state of the animal is the existence of an exces- 

 sively long filament extending from above the eyes 

 and in front of the corselet : this is rough with minute 

 spines, and appears, as Mr. Couch says, to be hollow. 

 Two similar filaments, equally long, are attached to 

 the posterior part of the corselet above the tail. 

 From the repeated and careful observations of Mr. 

 Couch there can be no doubt of their correctness, for 

 he not only bred them repeatedly in filtered water, 

 but succeeded in artificially extracting some from the 

 ova.* 



The metamorphosis in the Macroura generally is less 

 strongly marked than in those forms to which we have 

 hitherto referred. Of these, the lobster, Homarus, the 

 spiny lobster, Palinurus, the prawn, Palemon, and the 

 shrimp, Crangon, have been more or less fully observed. 

 Mr. Brightwell did not consider the changes which he 

 observed in the lobster such as to warrant the application 

 of the term metamorphosis ; but even Mr. Rathke him- 

 self, whose researches in the river 

 species have offered the strongest 

 arguments to the opponents of this 

 view, in his subsequent Memoir, 

 adduces this, amongst other spe- 

 cies, as an attestation of the truth 

 of Mr. Thompson's theory. Mr. R. 

 Couch's figure (fig. i) of the young 

 lobster on its exit from the egg 

 does not differ materially from that 



Fig. i. 



* The larva of Galathea is figured at p. 203, in illustration of Mr. R. Couch's 

 description at the previous page. 



