MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 263 



after which the monads disintegrate Hberating the contained oil 

 and fat drops which cause offensive odors and tastes (Uroglenopsis 

 americana, Calkins). In Vnxjlena the several monads are con- 

 nected with the interior of the colony by long basal threads. Chro- 

 matophores one or two; nutrition holophytic, with tendency in 

 some forms to lose the chromatophores and live as animals. 



Sub-family Lepochromonadince, Pascher.— These are the house or 

 test-dwelling ochromonads; the tests are extremel\' delicate with 

 the monads seated at the wider, open ends, or at the base, and with 

 or without a contractile stalk. The tests are frequently complex 

 owing to sculpturing or to superimposed growth rings (Dinohryon, 

 Hyalohryon, etc., Fig. 126). The genus Dinohryon is remarkably 

 rich in forms and is one of the most common genera found in fresh 

 water. Some species are solitary, others colonial with highly diver- 

 gent types of arboroid colony formation, the bases of the younger 

 tests attached to the inner sides of the older ones. In Hyalobryon 

 the tests are attached on the outsides of the older ones (Fig. 19, 

 p. 40). 



Family 4. Coccolithophoridse, Lohmann.— This group comprising 

 the smallest forms of marine plankton, is characterized mainly by 

 the peculiar discs of calcium carbonate which make up the shells. 

 The shell pieces are in the form of either solid discoidal plates 

 (discoliths) or of funnel-like structures (tremaliths), the latter per- 

 forated by a distinct pore and bearing flattened plates at one or 

 both ends. The separate plates were known long before the 

 organisms which carry them and received the name of "coccoliths. " 

 Huxley at one time interpreting them as the skeletal parts of 

 Bathybiu.s. The structure of the monads is typical of the Chryso- 

 monadida, with one or two flagella, yellow chromatophores and auto- 

 trophic nutrition. 



The most complete observations on the Coccolithophorida? were 

 made by Lohmann, but obser\ations on the mode of reproduction 

 of these forms are lamentably fragmentar\' and unconvincing. 

 Division through the main axis as in other C'hrysomonadida is 

 indicated, and there is some evidence of heteromorphic shells 

 (macrotheca and microtheca, Lohmann). We follow Ivohmann in 

 distributing the genera between two sub-families. 



Sub-family Syracosplioerinae, with individuals provided with one 

 or two flagella and with shells made up of imperforate calcareous 

 discs. 



Sub-family Coccoliiltophorincp, with individuals provided with one 

 flagellum and with shells made up of perforated discs which may 

 be simple or provided with hollow tubular processes, pipe-like or 

 trumpet-shape in form. 



Family 5. Silicoflagellidse, Borgert.— The genera and species of 

 this Family, found only in the sea, are characterized by the presence 



