10 THE VOYAGE OF H.M.S. CHALLENGEE. 



Synopsis of the four Faviilics of Collodaria. 



f Solitary cells, living as isolated individuals {Col- 

 Suborder I. COLLOIDEA. I loidea monozoa), . . . .1. Thalassicollida. 



Skeleton entirely wanting. 



J 



Associated cells, living in colonies or ccenobia 



{CoUoidea polywa), . . . .2. Collozoida. 



Suborder II. BELOIDEA. f Solitary cells, living as isolated individuals {Beloidea 



monozoa), . . . . .3. THALASSOsPHisniDA. 



Skeleton composed of. numer- j 

 ous needles or spieula, 

 scattered in the calymina. 



Associated cells, living in colonies or coenoLia 



(Beloidea yolyzoa), . . . .4. SPHiEEOZOiDA. 



Suborder T. COLLOIDEA, Haeekel. 

 Defnition.—SvvuELi.ARiA without skeleton. 



The suborder Colloidea comprises all those Spumellaria in which no skeleton is 

 developed. The whole body is therefore soft — a true malacoma — and is composed only 

 of two essential parts, the central capsule and the enveloping extracapsulum. The sub- 

 order contains only two different families, the solitary Thalassicollida (or Colloidea 

 monozoa) and the associated Collozoida (or Colloidea polyzoa). Both families are 

 very nearly allied, and differ only in one single essential character : the solitary life of the 

 former, the social union of the latter. It seems to be merely in consec^uence of this 

 difference that the cleavage of the nucleus commonly takes place very late in the former, 

 very early in the latter. 



Therefore the full-grown Thalassicollida'' (till immediately before propagation) commonly 

 exhibit one single nucleus in the centre of the capsule, whilst in the CoUozoida the 

 capsule is distended by numerous small nuclei. In these latter the centre of the capsule 

 usually contains one large oil-globule, whilst in the former oil-globules are either 

 wanting, or scattered in large numbers in the endoplasm, or disposed in one layer on the 

 inside of the capsule membrane. 



In the solitary Thalassicollida each capsule is enclosed in its own peculiar spherical 

 calymma, whUst in the associated Collozoida all capsules of the colony are united in one 

 common, very voluminous calymma. 



Family I. Thalassicollida, Haeekel, 1862. 



Tlialassicollida, Ilaeckel, 1862, Monogr. d. Radiol., p. 246. 

 Thalassicollida, Haeekel, 1881, Prodromus, p. 469. 



Definition. — C o 1 1 o i d e a solitaria. 



The family Thalassicollida comprises aU solitary Spumellaria without a skeleton. The 

 oldest and best known form of this famUy is the genus Thalassicolla, as restricted by 



