86 PROFESSOR OWEN ON THE AYE-AYE. 



ileum enters, and it diminishes in diameter to the blind end, and, in most, rather suddenly 

 about halfway thereto, which has led to the comparison of the caecal half to the 

 ' appendix cseci,' especially of the human fcetus '. In the characters of the ca;cum, the 

 Aye-aye strongly manifests its Lemurine affinities : this gut is scarcely one-fifth the length 

 of the body from the muzzle to the tuber ischii, whilst in the Grey Squirrel the csecum 

 is half the length of the body. In this Rodent the large intestines are twice the length 

 of the body, but they are only one-fourth longer than the body in the Aye-aye. 



The small intestines are rather more than three times the length of the body in the 

 Aye-aye, while in the young Squirrel they are seven times the length of the body. 



The divisions of the liver are at, or nearly at, right angles to the surface of the gland 

 in the Aye-aye, as in the Lemurs ; in the Squirrel they are oblique and deeper, the left 

 lobe covering almost all the others. 



The tongue becomes a good test of affinity, owing to its well-marked characteristics 

 in the Rodents and Lemurines respectively. The Squirrels, like other Rodents, have 

 a short tongue, thick vertically, and especially between the molar teeth, where the 

 dorsum rises above the tip, forming the ' intermolar lobe,' which commonly bears the 

 impress of the palatal furrows. 



In the Aye-aye there is no structure like this : the tongue is thickest transversely, 

 has a longer portion free, and, above all, it is characterized by the sublingual firm plate, 

 corresponding in general form and structure with that in other Lemuridce ^. 



The small median supra-thyroid laryngeal sacculus is an indication of the quadru- 

 manous nature of Chiromys. 



In the vascular system, the disposition of the great veins entering the heart affords 

 a test of the affinities in question. In the Sciuridcs, as in most other Rodents, the 

 left trunk of the jugular and subclavian veins passes down the back part of the auricle 

 to enter close to the orifice of the post-caval vein : in the Aye-aye, as in the LemuridcB 

 and all Quadrumana, that venous trunk crosses the fore part of the arteries rising from 

 the aortic arch to join the corresponding trunk on the right side and to form a true 

 ' pre-caval ' vein. 



The organs of generation are important indications of natural affinity in the Mam- 

 malian class, more especially the male organs, of which the sex of the Aye-aye dissected 



' " The caecum is long, and terminates almost in a point, and looks like the appendix cseci in the human, 

 especially the appendix in the foetus." — Hunter, 'Posthumous Essays and Observations on Natural History, 

 Anatomy,' &c., 8vo, 1360, vol. ii. p. 33 {Stenops gracilis). Schroeder Van der Kolk and VroUk have made 

 the same comparison. " Mais il est bon d' observer que chez 1' enfant en has age et chez les authropomorphes 

 I'appendice vermiforme ressemble assez au prolongement en pointe du caecum chez le Stenops" ('Recherches 

 d'.inatomie Comparee, sur le genre Stenops,' p. 50). 



^ Hunter, in Lemur mongoz, L. : — " The tongue has a part underneath in shape like a bird's tongue, so that 

 it might be called double-tongued" {op. cit. vol. ii. p. 29). See Hunteriau Preps. Physiol. Series, Mus. Coll. 

 Chir., Nos. 1516, 1517, and 1518 ; Physiol. Catal. 4to, vol. iii. (1836) pp. 83 and 84 ; Burmeister, in Tarsius, 

 op. cit. 1846, p. 104. pi. 6. fig. 2 ; Van der Kolk and Vrolik, in Stenops, op. cit. p. 52. pi. 1. fig. 5 b. 



