776 HUXLEY AND HIS WORK. 



observe that even the existing Amphibia present us with almost every 

 degree of modification of the type, from such forms as the oviparous, 

 branchiate, small-lunged iSiredon and Menobranchus, which stand in the 

 same relation to it as Gymnura to the Eutheria, to the exclusively air- 

 breathing Salamanders and frogs, in which the period of intraovular 

 development, either within the uterus itself or in special receptacles, 

 may be as much prolonged as it is in the mammalia. 



"A careful study, on full materials, of the development of the young 

 of such forms as Hylodes will probably throw great light on the nature 

 of the changes which ended in the suppression of the branchiae and 

 the development of the amnion and of the extra-abdominal part of the 

 allantois in the foetus of the higher vertebrata." 



During the intervening years no discoveries of fossil forms substan- 

 tiating these inferences have been discovered. Among the ancient 

 vertebrates now known none appear to be more nearly allied to the 

 mammals than certain Permian animals representing a special order 

 named by Cope Theromorpha or (later) Theromora. As early as 1878 

 "the order Theromorpha was regarded by Professor Cope as approxi- 

 mating the mammalia more closely than any other division of reptilia, 

 and as probably the ancestral group from which the latter were de- 

 rived." 1 These views were subsequently developed in greater detail, 2 

 and appear to be entitled to much consideration. In this connection 

 it may be added that the difference between Huxley and Cope is less 

 than the terms in which they have been stated might seem to indicate. 

 The gap between primitive amphibians and reptiles is by no means as 

 great as between the modern types, and it may be doubted whether 

 the ancestors of the mammalian stock were members of the specialized 

 order defined as Theromorpha. Neither of the philosophers may be far 

 out of the way. 



X. 



Among the most important results of Huxley's investigations were 

 the discovery and approximately correct recognition of the nature of 

 the "peculiar gelatinous bodies" found in all the seas, whether extra- 

 tropical or tropical, through which the Rattlesnake sailed, and which 

 were named Thalassicola, precursors of radiolarian hosts afterwards to 

 be brought to light, and the perception of the comparative affinities of 

 the southern forms of astacoidean crustaceans and their contrast as a 

 group with the forms of the Northern Hemisphere. I must resist the 

 temptation to further enumerate the great naturalist's discoveries and 

 generalizations. 



A few words on the nature of his work may be desirable. And here 

 it may be admitted that Huxley was rather a morphologist in a narrow 



1 The Theromorphous Reptilia. (Am. Nat., Vol. XII, pp. 829, 830, 1878.) 



2 The relations of the theromorplious reptiles and the monotrcme mammalia. 

 (Proc.Am. Assoc. Adv. So., Vol. XXXIII, pp. 471-482, 1 plate, 1885.) 



