REPORT ON THE RADIOLARIA. 39 



Other forms were afterwards described by Miiller and by myself in 1862. 1 Further 

 investigations have shown me that some species of this family are among the most 

 common Radiolaria, and occur in astonishing numbers on the surface of all warmer seas. 

 But the number of different species is comparatively small, and their distinction is very 

 difficult, as all the different forms are very variable and connected by intermediate 

 forms a truly " transformistic " group. 



The only character sufficient for the constitution of genera in this transformistic 

 group is found in the form and composition of the spicula ; the very variable form 

 of the jelly-calymma and the enclosed central capsule being without value for 

 this purpose. But also the form of the spicula is very variable, and not always 

 constant. In some species the particular form of the spicula is transmitted by constant 

 heredity, whilst in others it is very inconstant, even in one and the same indi- 

 vidual. (Compare the remarks on variability in the general introduction.) 



As the number of various forms is rather great, it seems to be advisable to distinguish 

 the three following genera. 



Synopsis of the Genera of Sphcerozoida. 



A. Spicula all of one kind, simple or needle-shaped, . . . . .12. Belonozoum, 



B. Spicula all of one kind, branched or radiate, or geminate, . . , .13. Sphcerozoum. 



C. Spicula of two or more different kinds, partly simple, partly branched, . .14. Rliaphidozoum. 



Genus 12. Belonozoum^ n. gen. 



Definition. S phserozoida with simple needle-shaped spicula, which are neither 

 radiate nor branched. 



The genus Belonozoum comprises the Sphaerozoida with simple needle-shaped 

 spicula, and may be regarded as the colonial form of ThalassosphcBra or Thalassoplancta, 

 derived from these solitary Beloidea by multiplication of the capsules and union 

 in a common calymma. 



I 



1. Belonozoum bacillosum, n. sp. 



Sphcerozoum bacillosum, Haeckel, 1881, Manuscript. 



Spicula all simple rods, straight cylindrical, obtuse at both ends, quite smooth. Central 

 capsule pellucid, with one single central oil-globule. 



Dimensions. Diameter of the central capsule 0'08 to 012, length of the spicula 0'05 to 0'08. 

 Habitat. Central Pacific, Station 271, surface. 



1 Loc. cit., Taf. xxxii., xxxiii. 2 Belonozoum = Needle-animal ; 



