GENUS CODONELLA. 615 



or plicate ; cilia of the general surface long and fine, presenting a tufted 

 or matted aspect, all directed towards the anterior extremity ; endoplast 

 laminate, nodular ; contractile vesicle single, spherical, anteriorly situated. 

 Length when extended 1-190". 



Hab. — Fresh water, parasitic within the intestinal and pulmonary 

 cavities of various species of Cyclostoma. Geneva (C. & L.), 



Claparede and Lachmann, the discoverers of this remarkable form — which, 

 excepting for the presence of the fine cuticular cilia, closely resembles a Trickodina 

 — have recorded the existence, within its oral cavity, of two transparent triangular 

 plates of considerable size, but whose nature and use they did not succeed in 

 determining. They likewise observed in close proximity to and immediately above 

 the posterior sucker a solid cap-shaped body, to which might possibly be attributed 

 the function of a muscular apparatus for the elevation or depression of the subjacent 

 disc. The movements of the cilia of the general surface of the body are referred to as 

 exhibiting a tufted aspect and elegant undulating action resembling that of Opalma, 

 Conc/iophthims, and Plagiotoina. The species here described was found in countless 

 numbers within the intestinal and pulmonary cavities of Cyclostoma elcgans ; a 

 further investigation among other aquatic MoUusca will probably reveal the 

 existence of many closely related forms. Through the intermedium of Trichodinopsis 

 the Heterotrichous order is clearly connected with that of the Peritricha, as 

 represented by Trichodina and its allies. 



Fam. VI. CODONELLID^, S. K. 



Animalcules free-swimming, conical or elongate, inhabiting an indurated 

 sheath or lorica, to the inner wall of which they are attached by the more 

 attenuate posterior extremity; oral aperture terminal, surrounded by an 

 outer circle of long, flexible, tentaculiform cilia, and an inner circlet of 

 shorter, cirrate cilia or lappet-like appendages. 



The animalcules of this small family group are to be recognized by the presence 

 of the long tentacle-like cilia which form an outer fringe around the frontal border, 

 a type of structure which recurs again, however, in the smooth-bodied and conse- 

 quently Peritrichous genus Dictyocysta. Floating mouth downwards with these 

 tentaculiform appendages actively deployed in various directions, the resemblance of 

 these elegant Infusoria to minute Medusae is very striking. All the representatives of 

 this group as at present known are essentially pelagic. 



Genus I. CODONELLA, Haeckel. 



Animalcules conical or trumpet-shaped, solitary, free-swimming, highly 

 contractile, inhabiting a helmet- or bell-shaped lorica, to which they are 

 attached by their posterior extremity; the anterior region truncate or 

 excavate, forming a circular peristome having an outer fringe of about 

 twenty long, tentacle-like cilia, and an inner collar-like border or frill, which 

 bears an equal number of slender, lappet-like appendages ; entire cuticular 

 surface clothed with fine, vibratile cilia ; lorica imperforate, of chitinous 

 consistence, sometimes sculptured or mixed with granular foreign sub- 

 stances. Hab. — Salt water, pelagic. 



The several species referred to this genus were originally discovered by 

 Professor Haeckel in the Mediterranean, and described by him in an article 



