290 INSECTA. 



packed in parallel lines : each testis is composed of two fusiform parts 

 precisely similar to each other ; and from both ends of every one of 

 these, which are hollow, arises a narrow duct ; so that there are four- 

 teen pairs of ducts arising from the fourteen secreting organs. The 

 ducts all end in a common canal, which gradually becomes enlarged and 

 tortuous, and terminates by a distinct aperture in the vicinity of the 

 anus. Just prior to its termination, the common ejaculatory duct com- 

 municates with five accessory glands (fig. 143, 2, c, d d, e e), four of 

 which are intimately united until unravelled, while the fifth is a simple 

 caecum of considerable length*. 



(748.) The ovarian system of the female Scolopendra is a single tube 

 (fig. 143, l), without secondary ramifications, but receiving near its 

 termination the ducts of accessory glands, as represented in the figure. 



(749.) Some Scolopendrae (S. phosphorea) emit, in the dark, a strong 

 phosphorescent light ; and one species (S. electrica) is able to give a 

 powerful electrical shock to the hand of the person who inadvertently 

 seizes it. 



CHAPTER XII. 



INSECTA. 



(750.) THE word Insect has at different times been made use of in 

 a very vague and indeterminate manner, and applied indiscriminately 

 to various articulated animals f. In the restricted sense in which we 

 now use it, we include under this title only such of the HOMO- 

 GANGLIATA as in their perfect or mature state are recognizable by the 

 following characters, by which they are distinguished from all other 

 creatures. 



(751.) The body, owing to the coalescence of several of the segments 

 which compose their external skeleton, is divided into three principal 

 portions the Head, the Thorax, and the Abdomen. The Head contains 

 the oral apparatus and the instruments of the senses, including the 

 antenna? or feelers, which are articulated organs presenting great variety 

 of shape, but invariably only two in number. The Thorax, formed by 

 the union of three segments of the skeleton, supports six articulated 

 legs, and sometimes four or two wings ; these last, however, are fre- 

 quently wanting. The Abdomen is destitute of legs, and contains the 

 viscera connected with nutrition and reproduction. 



(752.) But insects, before arriving at that perfect condition in which 

 they exhibit the above-mentioned characters, undergo a series of changes, 



* Vide Cyclop, of Anat. and Phys., art. " GENERATION, ORGANS OP" (Comp.Anat.). 

 f The word Insect, derived from the Latin word Insecta, simply means divided 

 into segments. 



