OCEANIC TINTINNOINA OF LAST CRUISE OF CARNEGIE 



and anastomoses of these elements, also reticulations, 

 fenestrae, lacunae, and coccoliths. The actual dimensions 

 of the lorica are subject to correlation with physical factors 

 and do not lend themselves to more than general de- 

 scription. 



The lorica is used as the basis of cla.ssification, as is 

 the shell in the Foraminifera, Radiolaria, Dinoflagellata, 

 Mollusca, and Arthropoda, and the skeleton in the verte- 

 brates. The outstanding feature in the speciating process 

 and in generic differentiation in the Tintinnoina is the 

 play of behavior, of the movements of the differentiating 

 schizonts, in the distribution of the secreted material and 

 in its shaping into the generic and specific patterns. This 

 coordinated behavior on the part of the daughters begins 

 before the separation and continues beyond the period 

 of cytoplasmic discontinuity. Thus, the oral and aboral 

 ends of the lorica, the regions in contact with the proto- 

 plasm for the longest time at binary fission, are the most 

 importantly modified and constitute the regions of great- 

 est taxonomic significance. The specific characters are 

 largely these, and generic characters are found in the con- 

 sistency of the wall substance and in the general form. 

 The oral end is directed backward in locomotion, and 

 the aboral end meets the first shock of environment. The 

 former has usually outrun the latter in differentiation, 

 and this has developed, perhaps, in response to specific 

 modification in behavior rather than from surrounding 

 influences. 



The Tintinnoina constitute about 40 per cent of the 

 known ciliates, marine and fresh-water. Few marine 

 ciliates are nonloricate. Their freedom of movement and 

 the availability of food in the sea has doubtless led to a 

 wide evolutionary spread of these creatures. No sea is 

 without some representative of this suborder. In the 

 coldest waters of the Arctic and within the ice-bound 

 Antarctic these animals are fully at home. They reach 

 their greatest differentiation in kind, however, in the 

 warm waters of the equatorial regions of the ocean. Here 

 there are hundreds of kinds in every plankton catch. 

 Especially within the upper levels of these warm seas; 

 where Coccolithophoridae are frequent and light pene- 

 trates freely, do these creatures abound. 



Acknowledgments 



Acknowledgment is made to the Carnegie Corporation 

 of New York for funds with which to complete the plate 

 and the figures. Mr. H. W. Graham, and Dr. }. A. 

 Fleming, Director of the Department of Terrestrial Mag- 

 netism of the Carnegie Institution of Washington, gave 

 help from time to time. Mrs. A. Abernathy assisted in 

 the execution of the finished drawings. The writer's 

 wife was an invaluable assistant in many ways, and the 

 administration of St. Mary's College offered sympathetic 

 aid. Without all these, the preparation of this report 

 would have been hindered. 



