OBSERVATIONS ON THE GANNET. igi 



Description of the Insect which inhabits the cel- 

 lular membrane of the Gannet. 



Ovate-oblong, smooth, glossy, white, with 

 eight short legs, furnished with several joints, and 

 terminated by bristles ; two on each side approxi- 

 mating, and near to the anterior end ; the others 

 similarly disposed, about one-third of its length 

 from the posterior end : of the posterior legs, the 

 hindmost pair is furnished with a very long 

 bristle, the other pair usually with two ; the an- 

 terior legs possess several bristles each. No 

 other appendages were discernible under the best 

 constructed microscope, not even the mouth or 

 eyes could be clearly ascertained ; but beneath, 

 at the anterior end from whence the fore-legs 

 arise, there are four light depressions, surrounded 

 by dark lines, in the two hindmost of which is a 

 dark spot, but these had not the appearance of 

 eyes : behind this part, is usually a fold in the 

 skin, at which place there is an independent mo- 

 tion : the feet are also observed to be in continual 

 alternate motion, while under the microscope. 



Size about that of Acarus siro, or cheese-mite, 



Pl. VII. Fig. I. Under part. 



2. Upper part, 

 3 Side v iew. 

 (All greatly magnified). 



As far as I have hitherto observed, this in- 

 sect is peculiar to the gannet, and does not ap- 

 pear to inhabit any other part than the cellu- 

 lar membrane : in some subjects, it is found in 

 prodigious abundance, together with the ova; 



