REPORT ON THE E.ADIOLARIA. clxxxi 



pliylogenetic conclusions which he drew from it, he arrived at an improved systematic 

 arrangement in which he distinguished six orders: (l) Thalassicollea, 

 (2) Sphserozoea, (3) Peripylea, (4)Acanthometrea, (5) Monopylea, 

 (6) Tripylea. The numerous isolated discoveries with which Hertwig enriched the 

 morphology of the Radiolaria, have been already alluded to in the appropriate paragraphs 

 in the anatomical portion of this Introduction (see L. N. 42, pp. 340, 341). 



The new and interesting group, which was thus erected into an order under the 

 name TRIPYLEA, I had already a year previously separated from the other Radiolaria 

 as " Pansolenia " in my Protistenreich (L. N. 32, p. 102). Since, however, neither 

 the three capsular openings of the TRIPYLEA nor the skeletal tubes of the 

 Pansolenia are present in all the families of this extensive order, I substituted in 1879 

 the more suitable name PH^EODARIA, which is applicable to all members of the group 

 (L. N. 34). In the preliminary memoir then published regarding the Phseodaria, a 

 New Group of Siliceous Marine Rhizopods, I distinguished four orders, ten families, 

 and thirty-eight genera. The great majority of these new forms (among which were no 

 less than 465 different species) were first discovered by the deep-sea investigations of the 

 Challenger. John Murray was the first who called attention to the great abundance 

 in the deep sea of these remarkable Rhizopods, and to the constant presence of their 

 peculiar, dark, extracapsular pigment body (phseodium) ; even in 1876 he described a 

 portion of them as Challengerida (L. N. 27, p. 536 ; L. N. 53, p. 226). The earliest 

 observations on the PHSEODARIA were made at Messina in 1859, where I examined five 

 genera of this remarkable group alive (compare p. 1522 and L. N. 16). 



By the discovery that the PHSEODARIA, although differing in important respects 

 from the other Radiolaria, still conform to the definition of the class, a new and extensive 

 series of forms was added to this latter, and by their closer investigation a fresh source 

 of interesting morphological problems was disclosed. In other groups, however, 

 morphology was advanced by comparative anatomical studies. In addition to the 

 smaller contributions of various authors, mentioned in the foregoing bibliography, I 

 may specially refer to the valuable Beitrage zur Kenntniss der Radiolarien-Skelete, 

 insbesondere der der Cyrtida by 0. Biitschli (L. N. 40, 1882). On the basis of careful 

 comparative anatomical studies, investigations into the skeletal structure of a number of 

 fossil Cyrtoidea and critical application of the recently published researches of 

 Ehrenberg into the Polycystina of Barbados (L. N. 25), Biitschli attempted to derive 

 the complicated relations of the Monopylean skeletons phylogenetically from a simple 

 primitive form, the primary sagittal ring. Even if this attempt did not actually 

 solve the very difficult morphological problem in question, still the critical and synthetic 

 mode in which it was carried out deserves full recognition, and furnishes the proof that 

 the comparative anatomy of the skeleton in the Radiolaria not less than in the 

 Vertebrata, is a most interesting and fruitful field of phylogenetic investigation. A 



