ON THE OUTLOOK OF VERTEBRATE MORPHOLOGY. 75 



the animal cell. The differences between the Protozoa and 

 Metazoa to-day appear to be certainly non-qualitative, 10 

 and the essence of organisation, as Whitman has lately 

 pointed out, 11 appears to no more lie in the " number of 

 nuclei than in the number of cells," while " comparative 

 embryology reminds us at every turn that the organism 

 dominates cell-formation, using for the same purpose one, 

 several, or many cells " ; and the view that the part played 

 by cell-division in the mere formative processes of the 

 animal body is the all-important one that it at first sight 

 appeared is on the decline. 



Midst this changing scene, recent investigations, such 

 as those of His, 1 ' 2 Duval, 13 Hochstetter, 14 Mitsukuri, 15 and 

 Beard, 16 have shown that, on the most rigidly definable 

 embryological grounds, the vertebrate remains, to say the 

 least, as interesting and important as the invertebrate. 

 Palaeontology has yielded us, in the Eotetrapoda 17 of 

 Credner, a group of animals which so completely unite the 

 Rhynchocephalia with the Stegocephala, that it is a question 

 whether the line must not be drawn between the former and 

 other lizards rather than between the Lizards and Amphi- 

 bians ; and in the Myxinoid Palceospondylus, 1 * with its 

 calcified notochord, it has unearthed the remains of . a 

 creature fit to rank in importance with Archceopteryx and 

 the Odont omit lies. The discovery of the Australian Mole 

 Marsupial Notoryctes™ in revealing to us a unique example 

 of isomorphism and convergence in nature, has emphasised 

 a far-reaching principle which there is reason to believe 

 has been too generally overlooked ; and the recent dis- 

 covery of lungless Salamanders in America 20 (if true), and, 

 in Burma, of a snake having the external appearance of 

 a harmless Colubrine, but the mouth of a viper, 21 would be 

 hard to beat, among the sensational and unexpected ; while 

 the recognition of two new vipers within the European 

 area is a theme with a sufficiently obvious retrain. 



It will thus be seen that the vertebrate morphologist has 

 reason for sustained confidence in his subject, and ample 

 reward for his loyalty. The course of advancement has, 

 within the period named at the outset, revolutionised his 



