His most important memoirs, besides that just mentioned, are those on the anatomy and classification of Fishes, on the Caecilians and on the developmental history of the Echinoderms.
They present a strong family likeness which is not found in any other terrestrial vertebrated animals with exception of some lizards and possibly Caecilians amongst the Amphibia.
P. 72), added the Caecilians, he named the three groups Apoda, Ecaudata and Caudata.
It has been attempted of late to do away with this order altogether and to make the Caecilians merely a family of the Urodeles.
If the absence of limbs and the reduction of the tail were the only characteristic of the group, there would be, of course, no objection to unite the Caecilians with the Urodeles; but, to say nothing of the scales, present in many genera of Apodals and absent in all Caudates, which have been shown by H.
The fourth category is represented by the Apoda or Caecilians in which, as we have stated above, the male is provided with an intromittent organ.