REPTILIA. 



321 



with recurved spines (fig. 233, &). Essentially, 

 these organs are merely a derivation from or 

 a modification of the skin, which is here lined 

 with erectile tissue. When in a state of re- 

 pose, these organs are inverted and retracted 

 beneath the skin of the tail, immediately 

 behind the anus. 



Each penis is provided with a special mus- 

 cle derived from beneath the first caudal 

 vertebra ; this muscle is inserted into the 

 bottom of the pouch when the organ is re- 

 tracted, and serves to retain it in this posi- 

 tion. 



The contraction of the muscles of the tail 

 contributes with the state of erection to make 

 them protrude from the opening of the cloaca. 



It seems to be an axiom universally ap- 

 plicable, that in those genera of reptiles 

 having the external opening of the cloaca 

 placed transversely, a double penis exists, 

 constructed upon the principle above de- 

 scribed. 



Each lateral penis has a longitudinal groove 

 that extends from its base to its extremity, 

 the extremity of which, when the organ is in 

 a state of erection, is continuous with a 

 groove in the cloaca. 



In those reptiles that have the extremity of 

 the penis bifurcated, as, for example, rattle- 

 snakes (fig. 233, k), the urethral groove! like- 

 wise bifurcates, sending a branch along each 

 division as far as its extremity. 



The armature of the glans varies in dif- 

 ferent genera; sometimes it is smooth or 

 simply covered by papilla?, or it may be covered 

 with 'finely pointed spines or cartilaginous 

 plates. 



Female Generative Organs. The reproduc- 



Fig. 240. 



Female Generative Organs of Lizard. 



a, ovaria; b, meso -oviduct ; c, opening of fal- 

 lopian tube; d, oviduct; e, ova contained in ovi- 

 duct ; f, termination of oviduct ; g, rectum ; h, 

 cloaca. 



tive organs in the female reptilia are con- 

 structed upon a plan of great simplicity, 

 consisting merely of the ovaria and oviducts, 

 through which the eggs are conducted out of 

 the body. The ovaria are two in number, 

 and are found situated upon the sides of the 

 spine in the thoracico-abdominal cavity, where 

 they are suspended by a fold of peritoneum, 

 by which they are invested ; they are situated 

 VOL.IV. 



further backward or forwards in the different 

 orders, according to circumstances. In the 

 Chelonians they are symmetrical upon the two 

 sides, and their shape is flattened, broad, and 

 short; but in the elongated bodies of many 

 lizards, and more particularly in the Ophidians, 

 these organs are long and narrow, and their 

 right ovary is situated considerably in advance 

 of the left. 



The ovaria of reptiles are constructed in 

 accordance with two different types, each of 

 which will require notice. In the Chelonians 

 the structure of the ovaria resembles that of 

 the birds, and has a racemose appearance ; 

 the ova, as their development proceeds, be- 

 coming pedunculated, so that they hang like 

 a bunch of grapes, by pedicles formed from 

 their calyx ; this capsule, when the egg is 

 mature, becomes lacerated along a line that 

 divides the globular ovum, like an equator, 

 into two hemispheres, exactly as in birds, and 

 the ovum escapes into the abdominal cavity, 

 there to be taken up by the oviduct. 



In the second type of structure, the ovary 

 forms an elongated sac or tube, in the delicate 

 walls of which the ova are developed. As 

 the ovules become matured, they project more 

 or less into the cavity of the ovary ; and when 

 they break loose it is into that cavity they 

 escape, and ultimately make their exit through 

 an opening that is formed at its anterior ex- 

 tremity for that purpose at the proper period. 

 In the former of these kinds of ovary the 

 ovules, in order to escape, have to rupture not 

 only the proligerous membrane or calyx, but 

 also the peritoneal tunic, with which they are 

 enveloped. In the second form, which is com- 

 mon to the Ophidians, the ovules have only 

 to tear through the proligerous membrane, in 

 order to escape into the cavity of the ovary, the 

 peritoneal covering of which gives way at the 

 proper season to allow them a passage out. 



The oviducts are invariably two in number, 

 and at their commencement are, as in all other 

 vertebrata, completely detached from the 

 ovary. Each oviduct is a membranous tube 

 which is connected by means of a broad me 

 senteric fold of peritoneum to the side of the 

 vertebral column ; it commences by a wide 

 aperture, by which the ovule is taken up ; 

 its walls are at first extremely thin and deli- 

 cate, but subsequently become thicker and 

 present a glandular appearance. The ovi- 

 ducts of reptiles are proportionally longer than 

 in birds, but they are much puckered and 

 folded up when in the unimpregnated state. 

 Each oviduct is retained in situ by a broad 

 peritoneal fold, which performs the functions 

 of a mesentery. 



The two oviducts in all reptiles open sepa- 

 rately into the cloaca, which thus represents 

 the vulva of mammiferous animals, giving 

 passage to the ova, and likewise receiving the 

 seminal fluid of the male during copulation. 



During the passage of the ovule through 

 the oviduct, it progressively becomes fur- 

 nished with additions to its structure, the 

 formation of which is due to the oviduct itself; 

 a circumstance which will account for the ex- 



