910 



PENIS. 



The class Insecta is dioecious, and an intro- 

 mittent organ is a common character throughout 

 the entire race. In some insects, as in Aphis, 

 the penis is double, and in the greater number 

 it is associated with special organs, termed 

 clampers, which assist in the impregnating act. 



The greater number of molluscous animals are 

 inhabitants of the deep, and amongst them 

 considerable diversity, as respects mode of 

 generation, exists. Some are hermaphrodite 

 in organisation, and self impregnating; others 

 are hermaphrodite and mutually impregnating; 

 a considerable proportion are dioecious, the 

 male and female apparatus being on different 

 individuals, and the impregnating fluid being 

 conveyed by the medium in which they live 

 from the male to the female animal; while 

 some few are dioecious and impregnate by 

 mutual concurrence. The air-breathers, or 

 Pulmonary Mollusca, are all hermaphrodite 

 and impregnate by reciprocal coitus. The two 

 last alone of the preceding modes of impregna- 

 tion are those in which a true intromittent organ 

 is required ; hence, although rudiments of a 

 penis may be discovered in many Mollusca, it 

 is only in the mutually impregnating herma- 

 phrodites and in the concurring dioecia that it 

 attains a size sufficiently bulky to render it an 

 important character. Thus in the class Tuni- 

 cata, which for the most part comprises self- 

 impregnating hermaphrodites, no intromittent 

 organ has been described. In the inhabitants 

 of bivalve shells, which are either self-impreg- 

 nating hermaphrodites, as the Oyster, or medi- 

 ately impregnating dioecia, as the fresh-water 

 Mussel, Anodonta, there is no penis. The 

 marine Gasteropoda are dioecious; some, as 

 the Patella, impregnating their females through 

 the medium of the sea water by which they 

 are surrounded, and others, including the whole 

 of the Pectinibranchiata, impregnating imme- 

 diately, being provided with a large penis for 

 that purpose. In the genus Trochus the vas 

 deferens terminates at the root of the penis, 

 and the latter is grooved ; and in Carniaria the 

 intromittent organ is bifid as well as grooved. 

 In the Pulmonary Gasteropoda, as the snails 

 and slugs, the generative organization is her- 

 maphrodite, impregnation being reciprocal, and 

 the penis of very large size. Among En- 

 cephalous Mollusca, as in Pteropoda, the orga- 

 nisation is also hermaphrodite, and the penis 

 of large size. In Cephalopoda, the highest 

 class of molluscous animals, the generative 

 structure is dioecious, but the penis is not 

 intromittent. The penis in Sepia and Octapus 

 is short and rudimentary, and pierced by a 

 canal for the transmission of the seminal se- 

 cretion ; but in the hooked Calamary the organ 

 is simply grooved along its under part. 



In passing from the higher invertebrata to 

 the class of Fishes we meet with a degradation 

 of organization as regards the generative system. 

 The penis, which we have seen to be properly 

 formed for intromission in several of the inver- 

 tebrate classes, is reduced to a mere papilla 

 on the surface of the cloaca in fishes. In the 

 Viviparous Blenny, however, in which internal 

 impregnation takes place, the penis is larger in 



size, and is probably increased in length during 

 coitus by eversion of the mucous lining of the 

 vas deferens. In some of the higher cartilagi- 

 nous Fishes it is interesting to remark that the 

 rudimentary state of the penis is compensated 

 for by the developement of an apparatus which 

 seems intended to secure the contact of the 

 cloacae for an appreciable time. This apparatus 

 consists of a pair of clasping organs, a provi- 

 sion to which we have already had occasion to 

 advert when speaking of the generative organs 

 of insects. 



In Amphibia, as in Fishes, impregnation is 

 effected by means of a close approximation, 

 and in most instances by contact of the cloacae. 

 There is no penis, but as a substitute for this 

 organ the male animal is possessed of an orga- 

 nisation fitted to maintain an embrace for a 

 considerable period. 



The penis of the Ophidian group of Reptiles 

 is a true intromittent organ, and remarkable for 

 the peculiarity of its structure. It consists of 

 two coecal processes, developed from the cloaca 

 at its posterior part, and extending back into a 

 cavity prolonged for a short distance towards 

 the tail. These cceca are lined by a horny pa- 

 pillated epithelium; they are invested with a 

 moderately thick layer of erectile tissue, and 

 have proper muscles attached to their extre- 

 mity. When the animal is excited by the vene- 

 real orgasm the turgescence of the erectile tissue 

 causes the eversion of the cceca and their pro- 

 trusion through the aperture of the cloaca. 

 Restored to the state of repose, they are re- 

 tracted by their muscles, and drawn back into 

 their original position. In the Rattlesnake a 

 singular modification of the intromittent organ 

 occurs, in the bifid termination of each of the 

 coeca. We cannot view the peculiarity of struc- 

 ture exhibited by Ophidia, without recalling to 

 mind the similarly inverted disposition of the 

 intromittent organ, which we have already seen 

 among the Invertebrata, namely, in Arachnida. 



The Lacertine Sauria are possessed of an in- 

 verted intromittent organ, similar to that of 

 Ophidia. In the Crocodile, however, the penis 

 is no longer an inverted ccecal pouch ; it is 

 grooved along its under part, attached by two 

 crura to the pubic bones, and furnished with a 

 rudimentary glans at its extremity. But even 

 in the Crocodile there exists a peculiarity of 

 structure which allies the family with the lacer- 

 tine Sauria and Ophidia. The structure to 

 which I allude, is a canal which is prolonged 

 from the peritoneal cavity for a short distance 

 into the substance of the penis, and there ter- 

 minates by a ccecal extremity. 



In Chelonia, the same kind of intromittent 

 organ occurs as is found in Crocodiles, a grooved 

 penis contained within the vestibule of the 

 cloaca, attached to the pubic bones, and hol- 

 lowed by one or more peritoneal canals. An 

 important difference, however, is met with, when 

 we compare the two groups of Chelonia, the 

 marine and the laud tortoises. In the former, 

 scarcely any obstruction to impregnation results 

 from the covering of the animal; the penis is 

 consequently small. But in the land tortoise, 

 where the shell extends beyond the limit ot 



