120 Dr. Kitkl <))t llif Anatoniij 



teroiis and lepidopterous insects, there are no stigmata, dis- 

 cernible at least either to the naked eye, or a common magni- 

 fying lens. 



But, to return to the stigmata of the gryllotalpa, the first in 

 order, beginning from the head, is situated very near the lower 

 part of the posterior ridge of the thorax. This stigma, not to 

 object to the term in the present instance, is apparently con- 

 nected with all the trachea? both of the thorax and of the head 

 itself. It dlHers remarkably in size and form from all the rest; 

 for instead of being a mere dot or point, it is an elongated fis- 

 sure, bounded by two horny lips. The second stigma, which 

 somewhat resembles in form, though of much less extent than 

 the preceding, is situated immediately behind the root of the 

 middle leg ; the third, which is still less than the second, is si- 

 tuated immediately behind the root of the posterior leg, near 

 the termination of the dorsal part of the third abdominal seg- 

 ment ; the fourth, fifth, and onwards to the tenth inclusive, 

 are situated near the terminations of the corresponding dorsal 

 segments of the abdomen. 



I would here notice by the way, a peculiar appearance very 

 constantly observable on the ventral surfaces of most of the 

 abdominal segments between the hind pair of legs and the 

 caudal antennae. At either extremity of those segments there 

 is a short line, not unlike that made by the stroke of a pen, 

 passing obliquely downwards aud inwards : it does not seem 

 easy to conjecture the use of these lines. 



1 may slate from repeated observations, that the stigmata, 

 taken generally, are not the terminations of single tubes : very 

 frequently two, and often more than two, tracheae originate 

 from the same stigma ; and very soon after the commencement, 

 one or even two of these tracheae subdivide into numerous 

 branches, which follow as nearly as may be the direction of 

 the original tubes. 



The distribution of many of the tracheae may be very satis- 

 factorily demonstrated by drying one of the insects under an 

 exhausted receiver containing muriate of lime : for after hav- 

 ing been thus dried the tracheae become perceptible to the 

 naked eye through the substance of the integuments. The fore- 

 going method of drying anatomical preparations may be suc- 

 cessfully employed on many occasions : it answers particularly 

 in the case of the human eye, or the eye of any sufliciently 

 large animal; for, in the act of exhaustion, the air contained 

 in the vitreous humour of the eye becoming expanded, pre- 

 serves the spherical form of the organ until the whole of the 

 moisture has been evaporated ; and it is then sufficiently firm 

 to support itself. 1 have traced most of the tracheae to the 



parts 



