J0LY 30, 1920] 



SCIENCE 



111 



19, No. 10, pp. 317-334, one plate, two text- 

 figures. February 13, 1920. 

 Professor Kofoid, the leading student of 

 the Flagellata, in a brief but important paper, 

 discusses convincingly the morphology and 

 relationship of Noctiluca. The data and 

 their bearing are well indicated in the 

 author's summary, as follows: 



1. Notiluca is a tentacle-bearing dinoflagellate 

 •with a sulcus, girdle, and longitudinal and trans- 

 verse flagella. 



2. The sulcus is longitudinal and midventral. It 

 includes the apical trough and the recessed oral 

 pouch and cytostome. 



3. The tentacle arises from its posterior end. 



4. The girdle has hitherto been overlooked. It 

 is a ehaUow trough at the left of the sulcus and at 

 right angles to it. It is seen best in small individ- 

 uals. 



5. The longitudinal flagellum is reduced and lies 

 within the oral pouch. The transverse flagellum 

 is represented by the prehensile tooth at the proxi- 

 mal end of the girdle at the left of the base of the 

 longitudinal flagellum. This organ exhibits struc- 

 toiral undulations and spasmodic or rhythmical con- 

 tractions. 



6. Distention by hydrostatic vacuoles, with flota- 

 tion replacing active locomotion, has led to degen- 

 eration of the flagella and their reduction in size, 

 and to the almost complete disappearance of the 

 girdle. 



7. Noctiluca belongs in the Noctilucidse, a family 

 of the tribe Gymnodenioidse, with Pavillardia, 

 another tentaculate, naked, non-ocellate dinoflagel- 

 late. 



8. There is no morphological justification of a 

 separate order of flagellates to hold Noctiluca, 

 such as the Cystoflagellata Haeckel. 



9. The Cystoflagellata may be retained as thus 

 emended to receive Leptodiscus and Craspedotella 

 pending discovery of their afiB.nities. 



Maynard M. Metcalf 

 The Oechakd Laboratory, 

 Oberlin, Ohio 



SPECIAL ARTICLES 



THE EFFERENT PATH OF THE NERVOUS 



SYSTEM REGARDED AS A STEP-UP 



TRANSFORMER OF ENERGY 



The properties of nervous tissue which fit 

 it for its peculiar role in the animal economy 



are given by Sherrington as (1) excitability 

 (2) spatial transmission of impulses and (3) 

 control of the liberation of energy in con- 

 tiguous tissues. Pawloff and others have em- 

 phasized the role of the peripheral sense 

 organs as energy transformers, since the 

 energy of light or heat or sound is trans- 

 formed, by appropriate mechanisms, to the 

 energy of a nerve impulse. Lucas and Ad- 

 rian's all or none hypothesis of nerve con- 

 duction calls attention to another aspect of 

 the work of the nervous system as a trans- 

 former of energy. According to this hy- 

 pothesis, the nerve impulse conducted by any 

 single nerve fiber is at all times the maximum 

 impulse which it is capable of conducting. 

 The evidence in favor of this view appears to 

 be steadily accumulating, although there are 

 still conditions under which the energy rela- 

 tionships are not clear. The efferent paths of 

 the nervous system appear to me to furnish 

 additional confijmation of the general truth 

 of the hypothesis. 



Neurologists have frequently commented on 

 the relatively few nerve fibers in the main 

 motor tracts of higher animals, i. e., the 

 pyramidal tracts, as compared to the number 

 of fibers in the ventral roots of the spinal 

 nerves and the great mass of muscles to be 

 activated. According to von Monakow, Red- 

 lich, Schafer and others, fibers of the pyra- 

 midal tract do not end directly about the 

 cells of origin of the motor nerves, but about 

 some intermediate or intercalated cells in the 

 spinal cord. Von Monakow has supposed that 

 each of these intermediate cells comes into 

 relation, through the branching of its proc- 

 esses, with more than one motor cell in the 

 spinal cord. Furthermore, the axone of each 

 peripheral motor nerve may branch on its 

 way to its effector. There is a possibility, 

 therefore, that each descending fiber in the 

 pyramidal tract of the spinal cord may ulti- 

 mately be able to actuate several terminal 

 axones in the peripheral motor system. Sup- 

 IKJse that one pyramidal fiber may, through 

 the intercalated neurone, come into relation 

 with three cells of origin of peripheral fibers. 



