PROFESSOR OWEN ON THE AYE-AYE. 87 



by me permits this application. In all Rodents the peritoneal opening of the serous sac 

 of the testis is so wide, and the cremaster so large and so disposed, that the gland can be 

 withdrawn into the abdomen, and it emerges into a temporary sessile scrotum only under 

 the seasonal enlargement for procreation, which is considerable. Thus, the Rodentia 

 are ' temporary testiconda.' The Aye-aye has not this organization : the testes are 

 permanently ' scrotal ' after their passage out of the abdomen. 



The Squirrels, like other Rodentia, have distinct ' vesiculse seminales ' with thick 

 glandular coats : in the Leporida the vesicula is single, but large. The absence of 

 distinct vesicular bag or bags in the Aye-aye removes it from the Rodentia, whilst the 

 size and shape of the prostate ' and of Cowper's glands approximate it to the LemuridcB. 



More decisive testimony is given by the penis. The Squirrels and all Rodentia are 

 ' retromingents,' the penis being bent back suddenly upon itself, with the ' glans ' 

 lying in a prepuce which opens close to the anus. In the Aye-aye, as in the Lemuridcs 

 and other Quadrumana, the preputial sheath of the penis projects freely forward to the 

 extent signified by the Linnean character ' pendulous,' applied to the ' Primates ' 

 generally in the ' Systema Naturae.' 



§ 14. Conclusion. 



The pressure of daily duties and engagements has prevented my further unravelling 

 the structure of this little denizen of the woods of Madagascar. I should otherwise 

 gladly have pursued the investigation to a degree of completeness more nearly 

 approaching that of which Burmeisterhas left so admirable an example in his ' Beitrage 

 zur nahern Kenntniss der Gattung Tarsius,' 4to, 1846. Believing, however, that the 

 main points required for determining the moot relationship of Chiromys to the Mam- 

 malian orders had been looked to, I felt it due to zoologists to submit the results to their 

 judgment, without further delay. 



The first and, to my mind, most congenial reflection that arose on the survey of these 

 structures was their adaptive relations to the known way of life and favourite kind of 

 food of the Aye-aye. 



This quadruped is stated to sleep during the heat and glare of the tropical day, and 

 to move about chiefly by night. 



The wide openings of the eyelids, the large cornea and expansile iris, the 

 subglobular lens and tapetum, are arrangements for admitting to the retina, and 

 absorbing, the utmost amount of the light which may pervade the forest at sunset, 

 dawn, or moonlight. Thus the Aye-aye is able to guide itself among the branches in 

 quest of its hidden food. To detect this, however, another sense had need to be 

 developed to great perfection. The large ears are directed to catch and concentrate, and 

 the large acoustic nerve and its ministering ' flocculus ' seem designed to appreciate, 

 ' Hunter, in Sienops gracilis :— "The prostatic glands are two at the basis [or the gland is left there], like 

 the heart on playing-cards." (See Prep. Phys. Ser. Mus. Coll. Chir. No. 2564 ; Physiol. Catal. vol. iv. p. 101 .) 



