330 PHYSIOLOGY. 



into the vesica seminalis, and appears in both as a flocky matter, which 

 alcohol renders crumbly, and which is animated by infusoria of the 

 genus Cercaria, or others allied to it. According to SuckoAv *, they 

 resemble Volvox globator, but are more ovate ; but he probably over- 

 looked the thin tail, or it was perhaps torn away, which is constantly 

 the case, according to Nitzsch f> in the Cercarice which inhabit 

 fresh-water muscles, but, indeed, after these animalculae have quitted 

 the body of the muscle for the water. These animalcule (Sper- 

 matozoa, according to De Bar) are developed by equivocal gene- 

 ration by the sperm, which surpasses all other organic fluids in its 

 generative power, yet they must not consequently be considered as the 

 truly animating and impregnating power in impregnation, but merely 

 as a proof of the healthy and genuine quality of the sperm, as they 

 are not found in that of old subjects, or of abortions or bastards. 



During copulation, which the preceding paragraph has shown to take 

 place in insects by an actual connexion of the two sexes, this liquid 

 passes from the penis of the male into the vagina of the female, or, 

 according to Audouin's repeated observation, into the spermatheca, into 

 the neck of which the penis protrudes. This is probably the cause why 

 the majority of insects, particularly the Coleoptera, possess such large 

 organs of generation, and that the spermatheca is the last of all the 

 appendages of the female organs. I also think that the frequently 

 long duration of copulation in many insects may be explained by the 

 spermatheca receiving the sperm. For example, the testicle cannot 

 secrete at once as much sperm as is necessary to fill the spermatheca ; 

 it must, consequently, after the ejection of what is contained in the 

 vesica seminalis, secrete an additional quantity, which secretion is 

 promoted by the stimulus given to the whole body by the act of copu- 

 lation, and is only terminated when the testes are exhausted in the 

 production of semen. We may thence explain the entire enervation 

 and frequently sudden death of the male after copulation (as for 

 example, in Ephemera) ; the correlative size of the spermatheca with 

 the duration of the connexion, speaks also iu favour of the opinion of 

 its being a place for the accumulation of the semen, which some 

 physiologists are inclined to doubt. We invariably find in those insects 

 which are long in copulation, large and broad spermathecae, for example, 



* Heusingcr Zeitschr. f. d. Org. Phys. vol. ii. p. 261. 

 f Bi-itrng zur Infusorienkundc. Halle. 1817. 8vo. 



