44 NATURAL SCIENCE. July. 



Carpenter. It was, first, in the enlightened comparison with extinct 

 crinoids, in the elucidation of many palaeontological problems, and 

 in the true explanation of what to some might seem morphological 

 anomalies. Secondly, it was in the foundation of an exact termin- 

 ology, and the establishment of true systematic characters : the 

 multitude of unstalked crinoids, which might have confused a less 

 patient worker, enabled Carpenter to formulate certain laws with 

 regard to the branching of the arms and the mode of union of the 

 brachials, to adapt and improve the ingenious method of formulation 

 employed by Bell, and finally, to sort the various species into ten 

 groups for Antedon and eight for Actinometra, which have been of the 

 greatest assistance to subsequent workers. Each fresh step that I 

 take into the depths of my own ignorance enables me the better to 

 appreciate the learning of my dead friend, and as I rise once more 

 from the perusal of these magnificent volumes I feel that not the 

 least result of the " Challenger " Expedition was the field it afforded 

 to Herbert Carpenter for the exercise of his marvellous industry 

 and clear insight. 



The Echinoidea, though still abundant in both individuals, 

 species, and genera, are, like the crinoids, of great palaeontological 

 importance, and it is fortunate that they, too, were placed in the 

 hands of a zoologist who could illumine the study of both recent and 

 fossil forms by his own knowledge in both departments. 



When Professor Alexander Agassiz wrote his report, 297 recent 

 species were known, of which forty-nine were due to the "Chal- 

 lenger." One-third of these species had been discovered since deep- 

 sea dredging began, to which third the " Challenger " contributed 

 more than a half, also adding fifteen new genera. Moreover, seven 

 genera, previously known only from fossils, were found in the deep 

 sea. In his " Revision of the Echini," Agassiz had subdivided the 

 recent faunas of sea-urchins into six realms — Atlantic, Circumpolar, 

 Australian, Antarctic, Pacific, and American. The knowledge of 

 distribution gained by the " Challenger" caused these subdivisions to 

 lose some of their significance, but enhanced the importance of the 

 bathymetrical zones, especially the Littoral, Continental, and 

 Abyssal regions, on which Agassiz had already laid stress. It is not, 

 however, the pressure varying with depth that appears the important 

 factor, but rather the gradual spreading of life from the shore to the 

 abyss ; and so we find that those genera which extend from the 

 Littoral to the Abyssal region are those which date back to the 

 Cretaceous period, that those with more restricted range are not 

 older than the Tertiary, while those which extend only slightly 

 beyond the Littoral range are found only in the more recent Tertiary 

 periods. A similar result was seen to follow in the crinoids. In the 

 Littoral region temperature has some influence in separating the 

 diverse faunae, not, however, by its highest, but by its lowest limits. 



The knowledge gained from the deep-sea forms has also caused 



