34 NATURAL SCIENCE. . July. 



food supply of pelagic animals. In the variety and elegance of their 

 different shells, as well as in their morphological and phylogenetic 

 value, they surpass all other unicellular organisms that we know. 

 This is the more astonishing as the whole class was formerly regarded 

 as a rare curiosity: Huxley, in 1851, had given the first accurate 

 description of a few species of ThalassicoUa, and Johannes Miiller in 

 his last work, in 1858, united these with the polycystines and 

 Acanthometra under the name Radiolaria, having observed fifty living 

 species. The whole number of Radiolaria described in the 2,150 

 pages and 140 plates of my Report, is disposed in two sub-classes, four 

 legions, twenty orders, eighty-five families, 739 genera, and 4,318 

 species. This great number might easily be augmented by a diligent 

 observer who would employ another ten years in the study of the 

 Radiolarian ooze. Ernst Haeckel. 



The three large volumes just referred to by Professor Haeckel 

 are no less evidence of the industry and genius of that distinguished 

 naturalist than of the vast field almost untouched before this expedi- 

 tion. It must not, however, be supposed that the cataloguing and 

 arrangement of a great number of species is all that we owe to this 

 section of the " Challenger " Report. There are also the details of 

 geographical and bathymetrical distribution of the Radiolaria, and 

 their part in the composition of deep-sea oozes : a mass of evidence 

 bearing on the wider problems of physiography and geology. 



More than this, we have gained greatly in our knowledge of the 

 structure of the living animal. The demonstration of the complex 

 nature of the central capsule in higher forms ; of the parasitic, dark- 

 green cells, which in one section take the place of the better-known 

 Zooxantbellae ; of the peculiar chemical composition of the skeleton 

 in the Phaeodaria : these are all matters of the greatest interest and 

 importance to the zoologist. 



This increased knowledge of Radiolarian anatomy is especially 

 useful as giving a basis for a new main classification into certain 

 large groups, at once natural and convenient. Students of the older 

 text-books — and, still more, teachers of zoological classification — will 

 readily recognise the advantage of replacing the long lists of families 

 usually given in such works by the two main sections, Porulosa and 

 Osculosa ; and the division of these into Spumellaria and Acantharia 

 in the former case, and Nassellaria and Phaeodaria in the latter. 



A. Vaughan Jennings. 



Sponges. 



As regards the Sponges, the results of the "Challenger" 

 Expedition are of an importance which it would be difficult to over- 

 rate. The magnificent collection of well-preserved specimens was so 

 large and various as to require the labours of no less than six 

 naturalists, some of them working several years, for its investigation. 



