400 



THE ANIMAL KINGDOM. 



tarsal bones, but in Amir a the astragalus and calcaneum are always 

 lengthened like the other bones of the limb, and are united at each end. 

 A double centrale is often present in adult Urodela. In this order there 

 are generally four, in Anura five toes to the fore-foot, in both five toes to 

 the hind-foot. But reduction of the numbers occurs in Urodela. Indications 

 of a sixth ulnar digit and a sixth tibial digit are found in both Urodela and 

 Anura, and in the latter the sixth toe may be well developed. The toes are 

 webbed in Amira. The carpus and tarsus appear to have been cartilaginous 

 with rare exceptions in Stegocephali. 



The olfactory lobes are sessile, and in Amir a connected at their bases 

 (see p. 75). The cerebral hemispheres are relatively large, largest of all 

 in Gymnophiona, and are usually elongated. They are connected by an 

 anterior commissure. The thalami optici and the paired optic lobes are not 

 so clearly marked off from one another in Urodela as in A nura, where the 

 latter are large, and contain ventricles of considerable size. The cerebellum 

 is always a transverse bridge of variable breadth. The pineal gland is 

 saccular in the young Anuran, perforates the roof of the skull, and is 

 attached anteriorly to the skin. In the adult the cavity of the sac is 

 obliterated, and its walls become fibrous. The gland does not perforate 

 the cranium in Urodela, but its apex is attached to the cranial roof. The 

 infundibulum is of great length in Epicrium. All the parts of the brain lie 

 in the same plane. The most notable features in the cranial nerves are the 

 following. The roots of the olfactory nerves unite only distally in Pipa, 

 and not at all in Gymnophiona, where the dorsal and ventral bundles pierce 

 the ethmoid separately. The Gasserian ganglion of the trigeminus and the 

 ganglion of the seventh nerve remain distinct in Urodela, though united by 

 a nerve : they are closely approximated in a few Anura, but fused in the 

 majority. The auditory and facial have a common root. The ganglia of 

 the glossopharyngeus and vagus are united, and the nerves generally pass 

 out through the same foramen in the exoccipital. There is no spinal 

 accessory nerve, and the area supplied by the hypoglossal is supplied by the 

 first spinal nerve in the majority: by the first and second (Salamandra): 

 by the second (Pipa) or the second and third (Menobranchus). There is a 

 cutaneous branch of the trigeminus to the dorsal aspect of the head in some 

 Urodela, and in the tadpole of the Frog. Cutaneous branches of the vagus 

 exist also, taking a lateral course along the body. There are three such 

 nerves in the perennibranchiate Urodela, in Derotremata, and even in Triton, 

 but they are lost in Salamanders (? all) and Anura. In the latter, however, 

 a branch accompanies the pulmo-cutaneous artery. The membranes of the 

 brain and spinal cord have an abundance of pigment cells in their visceral 

 laminae, and deposits of crystalline calcium carbonate are observable on the 

 exterior of these membranes, and especially of their prolongations upon 

 the spinal nerves (p. 76). The nasal capsules are supported by a solid 



