INSECTIVORA. 



1005 



in consequence gradually increases in size, 

 so that it is at last seen to be attached to the 

 surface of the skin by a very narrow neck, 

 below which the remains of the socket and 

 theca are seen in the form of a small bulb." 

 ( t'ig. 454, a.) " A completely formed prickle or 

 quill cut longitudinally and magnified, shewing 

 that it is hollow and filled with a pithy sub- 

 stance, which is transversely disposed, so as to 

 divide the cavity into many sections." But the 

 defence of the animal against attack is not the 

 only object of this modification of the hair. 

 I have more than once seen a hedgehog run to 

 the edge of a precipitous descent, and without 

 a moment's hesitation throw itself over, rolling 

 itself up at the same instant, and on reaching 

 the bottom run off perfectly uninjured. It is 

 unnecessary to point out how perfectly this 

 habit is provided for by the elasticity of the 

 spines, dependent upon their structure, as ex- 

 hibited in the figure. The under parts of the 

 body and the limbs are covered with ordinary 

 hair. The Tenrec and other Erinaceada re- 

 semble the hedgehog in these respects, and 

 in some species the quills and hair are inter- 

 mixed. 



The mole, on the other hand, possesses hair 

 -of the softest and most flexible description. 

 In its subterranean galleries, which are not 

 large enough to allow it to turn round, it must 

 often be obliged to retreat backwards ; and the 

 hair therefore is so constructed as to lie equally 

 smooth in every direction. This has been sup- 

 posed to be effected merely by its growing ex- 

 actly perpendicular to the surface of the body ; 

 but it is in fact still more effectually provided 

 for by a remarkable form of the hair itself. 

 Each hair consists of three or four broader 

 portions connected by intervening portions of 

 extreme tenuity; so that there are several 

 points in the length of each hair which pre- 

 sent no appreciable resistance. The hair 

 of the shrews is similarly constructed, and in 

 each case it is to this structure that the pecu- 

 liar and beautiful softness which characterizes 

 it is owing. It is worthy of remark that the 

 colouring matter of the hair exists only in the 

 broader portions, the intermediate parts being 

 wholly colourless. 



V. Organs of reproduction. The repro- 

 ductive organs of the Insectivora offer, in 

 several instances, some remarkable peculiari- 

 ties. The subterranean life of many of these 

 animals renders the meeting of the sexes in 

 their natural haunts a matter of almost for- 

 tuitous occurrence ; and it is therefore neces- 

 sary that the sexual desire should in the male 

 be sufficiently powerful to force him as it were 

 to seek and pursue the other sex through all 

 the difficulties and disadvantages occasioned 

 by their peculiar habits. Hence we find that 

 in most of them the male organs are developed 

 to an extraordinary degree; and in the mole 

 the enlargement of the testes as the season of 

 pairing advances is as remarkable as it is in the 

 sparrow or in any other example of this sea- 

 sonal increase of those organs. Two incom- 

 patible statements have been made respecting 

 the testes in the mole. Cuvier asserts that 



they make their appearance externally during 

 the season of propagation. Blumenbach de- 

 clares that they belong to the true testiconda, 

 with the hedgehog, &c. The truth is, as de- 

 monstrated with his usual ingenuity by Geof- 

 roy St. Hilaire, that the testicles of the mole 

 never make their appearance externally, al- 

 though during the season of their greatest de- 

 velopement they would do so but for the 

 peculiar construction of the parts in which the 

 organs of generation in this animal are con- 

 tained; for the abdominal cavity extends be- 

 yond the pelvis, as far as the first four coccy- 

 geal vertebrae, which in fact do not, properly 

 speaking, in any degree constitute the tail, 

 which is formed only of the posterior seven 

 vertebrse, and the testes during the season are 

 protruded so as to lie concealed under this 

 portion of the caudal division of the spine, 

 which forms as it were a continuation of the 

 upper part of the pelvis. In the hedgehog the 

 testes remain within the abdomen excepting 

 during the spring, and even then they are but 

 little protruded. The object of their being 

 thus generally protected is obvious : in the 

 hedgehog these organs, if external, would be 

 exposed to danger from the act of rolling itself 

 up, and in the mole and its congeners they 

 would interfere with the act of excavating 

 their subterranean passages. The penis in the 

 mole possesses a remarkable peculiarity, which 

 doubtless has reference to the condition of the 

 female organ presently to be described. It 

 consists in a small terminal bony appendage, 

 covered but slightly by integument; it was 

 considered by Daubenton as the os penis, but 

 from its different situation it may be doubtful 

 perhaps if it be in truth analogous to that part. 



The male organs are in the hedgehog deve- 

 loped to an extraordinary degree, more espe- 

 cially the vesicula seminales. The testes are of 

 an oval form, smooth, and although large in 

 proportion to the size of the animal, are much 

 smaller than the vesiculae seminales ; these are 

 of enormous size, each consisting of four or 

 five fascicles of extremely convoluted tubes, 

 the membranous parietes of which are ex- 

 tremely thin and fragile. Cowper's glands and 

 the prostatic gland are also of considerable size 

 in this animal. The orifices of the vasa defe- 

 rentia, vesiculee seminales, prostatic gland, and 

 Cowper's glands all open within the foramen 

 ccecum of the urethra. 



The female organs in the mole offer some 

 peculiarities which deserve more attention than 

 they have hitherto received. 



In the first place, it appears that in this 

 animal the urinary and genital orifices are 



Fig. 455. 



