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Show 328 MR. W. WOODLAND ON TIIE [Apr. 2], hand to the jumping-shrews among the Insectivora." These animals, unlike the Macropodidae, move their hind limbs alternately in the process of walking. Unfortunately the writer has been unable to discover detailed information with regard to the testes in these groups. Other families are the clumsy, thick-set Hystricidae, the very active Castoridae (Beavers), Myoxidae (Dormice), and Muridae. During the rutting-season the testes of Rodents migrate more posteriorly than at normal times; but this merely indicates a slight displacement probably due to the periodic enlargement of the organ, the cremaster muscle effecting return by decreasing the capacity of the scrotal emergence. This can be well seen in the Muridae, where the slightest impact will cause a dislodgment of the testis. The order Insectivora comprises " small animals............of very low type............belonging to the oldest mammalian stocks............ which are generally terrestrial, although rarely of arboreal or aquatic habits............the greater number are cursorial." " In the subfamily Centetince, and Chrysochloris, the testes lie immediately behind the kidneys, but in others more or less within the pelvis; during the rutting-season they become greatly enlarged, forming protrusions in the inguinal region." The various families of tins group afford good illustrations of the correlation of impulsiveness with degree of testis transposition. As stated above, in the Centetince or " Crawlers "-the appellation denoting their mode of locomotion-and Chrysochloris, which is inactive and fossorial, the testes lie just posterior to the kidneys, i. e. are abdominal. In the companion subfamily, the Oryzorictince, the two genera are represented by small animals-Macrogcde being mouse-like with a long tail, and Oryzorictes mole-like in form. The testes are situated near the urethra. In the Erinacein'ce or Hedgehogs the testes are situated on the " underside of the inguinal canal." Their " movements are sluggish, their steps almost tottering, their gait clumsy." On the other hand, in the active Soricidae (Shrews) and saltatorial Macroscelidae (Jumping-Shrews), the testes project at the periphery of the perinaeum, and in the Solenodontidae, the feet of which are " formed for running," the " testes are received into perinaeal p o u c h e s ." In the order Chiroptera, the members of which are so highly specialised for flight, there is " no scrotum, and the testes are either abdominal or inguinal." " We find in the low organization of their brain a proof of their inferior status "-a fact otherwise implied by the absence of the scrotum, unless a secondary retention has occurred owing to the danger of partial externality involved in the conditions of flight and position of the hind limbs. The order Ungulata is subdivided into the Ungulata vera and the Subungulata. In the former suborder, needless to say, the testes of the large majority reside in a well-defined scrotum, corresponding to the eminent impulsiveness of the animals. In the Nasicornia (Rhinoceroses), however, the testes are inguinal, the tunica vaginalis communicating freely with the body-cavity. As |
