﻿120 CLEMENS' SYNOPSIS OF 



been noticed by entomological anatomists, I regret my inability to solve at present 

 the question of the function connected with it. 



Antennae. We have still to consider these organs in the perfect insect. As has 

 been mentioned heretofore, they are quite invariable in structure in the embryo, but 

 in the imago their variations and differences are exceedingly numerous: In the latter 

 state these organs consist of a bulb, and a stalk composed of many articulated joints, and 

 furnished with a variety of accessory appendages, amongst the various members of 

 the order. Within the head, the entire circumference of the bulb serves as the 

 point of attachment to numerous delicate muscles, but they are never extended into 

 the bulb itself. If there is any muscular tissue whatever, either within the bulb or 

 the antennal stalk, I have failed to ascertain the fact, or to recognize the tissue 

 beneath the microscope. The stalk is occupied chiefly, if not entirely, by a tracheal 

 trunk, and what, in the recent specimen, is a soft, pulpy, granular substance that 

 freely escapes under pressure. This, beyond doubt, is nerve tissue, and from it. is sent 

 a distinct branch, or rather a sheath, accompanied by a branch from the spiral 

 trachea to each pectination on the antennae of Samia Gecrqpia. These pectinations of 

 the stalk are furnished densely -with tubular, delicate cilia, on the inner surface of 

 which, doubtless, both the nerve and tracheal filaments ultimately ramify. This fact, 

 however, I have been unable to demonstrate by actual dissection, because of the 

 difficulty involved in the management of such minute isolated and opaque parts ; but 

 I regard it as none the less certain. As sensation according to a general law, mani- 

 fests itself in the ultimate ramifications of nerve tissue, the cilia of the antennas must 

 be regarded as the sensitive surface of this instrument. 



The antennae in other orders I have examined, do not differ materially in structure 

 from that of lepidoptera. In the Ichneumonidce we find an apparently simple stalk 

 externally, but it is really abundantly furnished with short, delicate, tubular hairs, 

 that open on the interior of the stalk by perfectly distinct orifices. Interiorly it 

 contains an apparently simple sheath of granular nerve tissue, a tracheal trunk and 

 no muscular tissue. Although in the rude process of disruption with the finest 

 needles, no processes from the nerve sheath to these delicate tubular hairs can be 

 detected, is it to be supposed that their interior is therefore unoccupied by them, and 

 that they are simply filled by the circulating fluids ? Notwithstanding this similarity 

 of structure, I do not think the function of the instrument is identical in the two 

 orders. It is, however, similar, and is an illustration of the ways and means by which 

 one function is carried out in different orders. 



Function cannot be determined from observation on structure alone. Experimental 

 observation must be united with it in order to obtain facts for our guidance. 



Every entomologist must be familiar with the fact, that when a moth singes its 

 antennas in a flame, it is more or less incapable of directing its flight, and usually spins 



