^28 



LECTURE XVIII. 



summer months. In the autumn the organs are somewhat changed 

 in form ; the terminal ovarian portion dilates into a clavate ccecal 

 extremity filled with numerous ova : the rest of the straight canal is 

 divided into two successive elongated elliptical chambers, the last 

 being the largest, and generally containing an elongated ovum which 

 is excluded as such. 



The fertility of an Insect is indicated by the length and number 

 of the egg-tubes. Seventeen ova have been counted in a single tube 

 in the queen-bee, which has more than a hundred of such tubes. 

 But her fertility is greatly surpassed by the queen of the Termite 

 communit}^ in which the abdomen expands to so enormous a bulk, in 

 order to include the ovaria, that the thorax and head seem like mere 

 appendages to its anterior part. She lays, according to Smeathman, 

 sixty eggs in a minute, and this rate is continued, with, perhaps, 

 intervals of repose, for several days. 



However various may be the form and structure of the ovaria, their 

 situation is nearly the same in all insects. They occupy the sides of 

 the abdomen, and, when fully developed, distend that cavity, leaving 

 space only for the intestine and the internal accessory parts of gener- 

 ation. They are connected together by the branches of the tracheae, 

 and, in many insects, are retained in their position more particularly 

 by delicate but firm filaments continued from the anterior extremity 

 of each ovarian tube, and ascending to become connected with the 

 thoracic aorta. Professor Miiller describes these filaments as opening 

 into the dorsal vessel. 



The oviduct varies in length and capacity : in the Hydrophilus 

 four filamentary blind canals are attached to each side ; but in most 

 insects the accessory glands communicate with the common canal 

 formed by the union of the two oviducts. The common canal has 

 usually a dilatation at its middle part, beyond which it receives the 

 tube of the spermatheca and the duct of the coUeterium or mucous 

 vesicle. 



Experiment has proved the office of the spermatheca {fig. 103, 6.) 

 to be that which its name implies.* By the application of the fluid 

 contained in it to the eggs of an unimpregnated female Hunter made 

 them fruitful : he also found that the intromittent organ penetrated 

 its canal, an observation which has since been confirmed by Andouin, 

 and other observers. 



The coUeterium i^fig' 103, c.) secretes the white gluten, with which 

 the impregnated eggs, when not developed in the body, are covered, 

 and by means of which they are cemented together and fastened to 

 other objects. In some insects, as the Tinece^ the mucous organ has the 



* See Hunter, Animal Economy, 8vo, 1837, p. 461. 



