1903.] TRANSPOSITION OF MAMMALIAN ‘TESTES. all 
in general is small. The Bradypodide are arboreal inhabit, 
and are characterised by ‘“ habitual sluggishness,” being ‘ most 
inefticient walkers,” and in climbing, never leaping from bough 
to bough (a form of activity involving more impulsiveness than 
even the gallop, but probably not more than that involved in 
saltation). Their testes are placed close to each other, lying on 
the rectum between it and the bladder; 7. e. are retained in the 
abdomen. The Myrmecophagide are also not noted for activity, 
and their testes are disposed as in the Sloths. The Dasypodide 
are similarly inactive, being ‘‘ harmless and inoffensive,” endeavour- 
ing to escape by rapid burrowing. However, it is stated that 
“they can run with great rapidity.” The testes are abdominal, 
lying “above the brim of the pelvis.” The Manide are terrestrial 
and burrowing in habit, but some members of the group can 
climb trees. They are not very active. The testes lie in the 
inguinal canal. The Orycteropodide (Aard-varks or African 
Ant-eaters) are terrestrial and fossorial. Their testes are 
“inguinal, but they appear to descend, at all events temporarily, 
into a scrotum.” Their phylogenetic position is uncertain. In 
the order Sirenia the testes, needless to say, are abdominal. 
These animals are “slow and inactive in their movements, mild, 
inoffensive,” browsing at the bottom of water. 
The piscine locomotion of the Cetacea sufficiently accounts for 
the abdominal position of their testes, which organs are placed in 
the proximity of the kidneys. Even assuming the terrestrial 
ancestor of the Cetacea to have been characterised by the exter- 
nality of the testes (which is improbable considering their existing 
localisation), such would inevitably have assumed an internal 
position consequent on the serious risk of injury involved under 
Cetacean conditions, 
The Rodents are comparatively small animals. In habit they 
are mostly terrestrial, but some are arboreal and some natatorial. 
“The testes in the rutting- season form projections in the groins, 
but (except in the Duplicident ita) do not completely leave the 
cavity of the abdomen,” 72.e. the scrotal elevations are not 
well-defined. The Duplicidentata comprise the Hares, Rabbits, 
and the Picas or Tailless aie all extremely active animals, 
the latter being described as “agile” and as living in crevices 
among rocks. The Siilicidontats comprise the. remaining 
Rodents, the principal families of which are the following :— 
The Sciuridee “ vary between the two extremes presented by our 
ordinary squirrels, the agile climbers, and the sluggish, clumsy 
marmots, which live almost entirely underground.” Assuming the 
sti stement to be correct that the condition of the testes is similar in 
each of these two divisions (which is doubtful), it is evident that 
the latter are specialised forms descended from active ancestors, 
The locomotion of the Dipodide resembles that of the marsupial 
Macropodidee and insectivoran Macroscelidee, ‘* The whole struc- 
ture is adapted for jumping, and we find resemblances in their 
structure on the one hand to the kangaroos, and on the other 
