372 Prof. J. van der Hoeven on the Genus Menobranchus 
which there are sixteen or seventeen vertebrae between the skull 
and the pelvis. 
We must therefore guard against expressing this relation 
too strongly; and, while asserting that the nearest affinity of 
the Menobranchus is probably with Proteus, we must, at the 
same time, admit it as intermediate between this and Crypto- 
branchus. I should incline even to regard Menobranchus as oc- 
cupying the central position in the ichthyoid group. In fine, 
we have in the present only another instance of what nearly 
always occurs in families and groups composed of but few spe- 
cies, and these spread over various and remote countries: there 
are almost as many genera as species; and, in spite of the com- 
mon bond of affinity, there is a very marked difference in the 
general form and in the proportions of the body and its parts. 
Those who would prefer to dispose the genera in a single 
series, might perhaps do so by allowing Siren to follow Cecilia, 
and the Axolotl to occupy a corresponding position on the other 
side leading to the Salamanders (Urodela with eyelids). .The 
ichthyoids afford a very interesting illustration of the proposi- 
tion that some animals present as permanent a form which is 
only transitory in others; and Lamarck might have said that, 
in the Axolotl, nature was on the point of forming the Triton. 
Cuvier already in 1807 made use of the happy expression larve 
permanente ; and it was in accordance with this that he said that 
the Siren might be regarded as a permanent larva of this family*. 
We should thus have the following succession :— 
Siren, 
Amphiumat, 
Proteus, 
Menobranchus, 
Cryptobranchus, 
Sirenodon, 
since at Rotterdam, the pelvis was found to be suspended, on the right, 
from the twentieth, and on the left from the twenty-first vertebra. (Aan- 
teekningen over de Anatomie van den Cryptobranchus japonicus, door Dr. 
F. J. J. Schmidt, Dr. Q. J. Goddard en Dr. J. van der Hoeven, Jun. : 
Haarlem, 1862, 4to, p. 11.) The authors of this memoir cite an observa= 
tion of C. A. Schultze, attesting a similar inequality or asymmetry as ob- 
served in the skeleton of a Triton cristatus. They might also have added 
that the anatomist Mayer had recorded a like circumstance with regard to 
the other species of Cryptobranchus, that from the Alleghanies. Although 
it would seem to be normal in this species that the pelvis be thus suspended 
from the twentieth vertebra, Mayer observed, in one of the skeletons pre- 
pared by him, that it adhered only on the left side to this vertebra, but on 
the right to the nineteenth (Analecten, &c. p. 78). 
* Recherches sur les Reptiles douteux, p. 109. 
+ These two genera depart more particularly from the true Salamanders 
