NARRATIVE. OF THE CRUISE. 221 



the view, afterwards corroborated, that the yellow cells, which are to be found in the 

 jelly round about the central capsule, do not belong to the organism itself, but are 

 parasites or rather ' Symbiontes,' like the Gonidia of Lichens. 



" The histology of the Radiolaria, which offers peculiar and difficult relationships, was 

 first interpreted by Professor Richard Hertwig, a pupil of Haeckel. He published, 'in 1 876, 1 

 the first accurate account and correct interpretation of their cell-nuclei, and demonstrated 

 that the whole organism, in spite of very peculiar modifications, is to be regarded merely 

 M a single cell. In his work, published in 1879, 2 Hertwig undertook a reformation of 

 the whole classification of the Radiolaria, based upon important discoveries with respect to 

 the structure of the central capsule, and divided the class into six different orders. 



"Meanwhile Professor Ernst Haeckel had, in 1876, commenced the investigation of 

 the extraordinarily rich material collected by the Challenger. The preliminary account 

 of his investigations, and the changes which they rendered necessary in the current 

 classification, were published by him in October 1881, 8 shortly before his journey to 

 Ceylon. He then distinguished twenty-four families, including 630 genera. In 1883 

 Haeckel expounded the relationship of these families, and their arrangement, on 

 phylogenetic grounds, in four primary groups. 4 



" Professor Biitschli gave, in 1882, 5 a good synopsis of all previous observations on the 

 Radiolaria, as well as a number of valuable original investigations upon their siliceous 

 skeletons. St. George Mivart had already, in 1877, given a short review of the sub- 

 ject in the Journal of the Linnean Society. 6 



" The morphology of the Radiolaria is now so thoroughly understood that we are no 

 longer in doubt as to their relationship to the other Protozoa. It is certain that they 

 are true Rhizopoda, distinguished from the other classes of this group (Foraminifera, 

 Heliozoa, Lobosa) chiefly by the remarkable separation of their unicellular body into 

 two principal constituents, namely, the inner ' central capsule ' and the externally situ- 

 ated ' extracapsularium.' 



" The important central capsule is a highly-organised cell, which is surrounded by a 

 special membrane, and encloses one or more nuclei in its protoplasm, and sometimes 

 other bodies in addition, such as oil-globules, crystals, pigment-granules, &c. At the 

 time of reproduction, numerous swarmspores are developed in it, which are set free by 

 the bursting of the capsule, and swim about by means of a flagellum. 



" The extracapsularium consists of a voluminous gelatinous ' involucrum,' which 

 encloses the central capsule, and numerous fine pseudopodia, which radiate through 



1 Zur Histologic der Radiolarien, Leipzig, 1876. 



2 Der Organismus der Radiolarien, Denkschr. d. med.-nat. Gesellsch. Jena, Bd. ii. p. 129, 1879. 



3 Jenaische Zeitschr., Bd. xv. pp. 418-472, 1881. 



4 Jenaische Sitzungsb., Feb. 16, 1883. 



6 Bronn, Klass. u. Ord. d. Thierreichs, Bd. i. Aufl. 2, 1882. 

 6 Journ. Linn. Soc. Loud. (Zool.), vol. xiv. p. 136, 1877. 



