624 ORDER PERITRICHA. 



membranous collar, whose contour is compared by its discoverer * to that of an 

 Elizabethan frill, is described as being in a state of constant vibration, alternately 

 closing up and expanding with a twisting movement, and exhibiting the same 

 rapidity and regularity in this motion as do a series of cilia in a similar position. 

 The movements of the collar may in short be compared to those of a series of cilia 

 united throughout their length by a delicate membrane, progress tlirough the water 

 being at the same time accomplished with the aid of this mechanism in a manner 

 closely analogous to the locomotion of the free-swimming Medusa. Unfortunately, 

 no note was taken at the time of the position or character of the endoplast or 

 contractile vesicle, nor of the reproductive phenomena. 



Fam. II. DICTYOCYSTIDiE, Haeckel. 



Animalcules free-swimming, secreting and inhabiting siliceous or cor- 

 neous, fenestrate or imperforate, helmet- or bell-shaped loricce ; peristome 

 terminal, subcircular, associated with a more or less complex ciliary- 

 system ; oral aperture eccentric, cuticular cilia entirely absent. 



The family of the Dictj'ocystidfe was originally instituted by Professor Haeckel t 

 for the reception only of Ehrenberg's genus Dictyocysta. To this is here added the 

 new generic group Petalotricha, including the so-called Tintiniius ampulla and Tin- 

 tinmis spiralis of Professor Fol, which differ from the true Tintinni, but resemble 

 Dictyocysta, in the non-ciliation of their cuticular surface and in the compound 

 character of the peristomal appendages. 



Genus I. DICTYOCYSTA, Ehrenberg. 



Animalcules solitary, free-swimming, extensile and contractile, excreting 

 and inhabiting more or less perforated, bell- or helmet-shaped, siliceous 

 loricse ; the enclosed body globular or campanulate, attached to or 

 dependent from the posterior extremity of the lorica, and protruding, when 

 extended, to some distance beyond its aperture, the oral or distal extremity 

 truncate, circular, bearing an outer fringe of long, tentacle-like cilia, and an 

 inner circle of short, thick, uncinate cilia or cirri ; oral aperture eccentric, 

 located close to the inner circle of uncinate cilia ; general cuticular surface 

 entirely smooth. Hab. — Salt water, pelagic. 



The animalcules of this genus closely resemble those of Codonclla previously 

 described, and but for the absence of fine cilia upon the general cuticular surface 

 would be necessarily placed in the same family. The singular anterior fringe 

 of lappet-like appendages is likewise wanting in Dictyocysta, being replaced by 

 a circlet of cirrose adoral ciHa, corresponding with those of the more ordinary 

 Peritricha. The beautiful perforated siliceous loricas of the various species are 

 scarcely to be distinguished from the tests of certain Polycistina;, and were indeed, 

 previous to the examination and report upon their living inhabitants by Professor 

 Haeckel, referred by Ehrenberg % to that Radiolarian group. 



Dictyocysta cassis, Hkl. Pl. XXXII. Figs. 29-31. 



Lorica helmet-shaped or inflated conical, about one and a half times 

 as long as broad, pointed posteriorly, gradually widening towards the 



* ' Quarterly Journal of Microscopical Science,' vol. xiii., 1874. 



t " Ueber einige neue pelagisclie Infusorien," ' Jenaische Zeitschrift,' Bd. vii., 1873. 



% ' Monatsbericht Berliner Akademie,' p. 236, 1854. 



