Maech 25, 1898.] 



SCIENCE. 



425 



Happily there is already a tendency to drop 

 many of these synonyms. Let it be hoped in 

 favor of neurocyte, neurite and dendrite, as 

 being the least cumbersome and more in har- 

 mony with other words denoting a part, as, 

 somite, sternite, tergite, phagocyte, etc., or as 

 already, as in the case of neurocyte, having 

 been thought by good authority sufficiently 

 common to be given a place in popular diction- 

 aries. 



This terminology, however, seems to be in- 

 sufficient for the needs of the study of the ar- 

 thropod nervous system, where the part of the 

 neurocyte containing the nucleus is situated on 

 the outside of the nervous system and con- 

 nected with the branching portions of the neu- 

 rocyte by a stalk or process of greater or less 

 length. It has always seemed misleading 

 and more or less cumbersome to speak of 

 this portion as the nerve cell, the cell, or the 

 cell body. For this reason it appears that, to 

 be in harmony with the other terms noted, that 

 part of the neurocyte that in the older literature 

 is called the nerve cell should be denominated 

 the neurocyto-somite, or, more briefly, cytoso- 

 mite. Such a term will not be misleading, nor, 

 since it is a compound of frequently used par- 

 ticles, will it be difficult to retain. 



In writing or speaking of the process just 

 mentioned originating from an arthropod or 

 spinal ganglion cell it has frequently seemed 

 as though time and energy might be economized 

 by giving this also a distinctive name. In- 

 stead of referring to a process from a neuro- 

 cyte, neurocytic process, or a bundle of pro- 

 cesses from such and such cells, it would be 

 much better to use the word neurocytocaulite,or, 

 briefly, caulite, which, along with cytosomite,'is 

 here suggested. It matters little whether some 

 one may be able to show that caulite has, as seems 

 probable, been used before in connection with 

 some other subject, for it denotes a part, and 

 the context in which it is used will prevent 

 misconception. Should, however, a possibility 

 of misconception arise, the difficulty may be 

 readily overcome by using the form cytocaulite. 



Summarizing the foregoing, the following 

 morphological definition may be given a neuro- 

 cyte : A cellular element of the nervous sys- 

 tem, consisting of a cytosomite containing the 



nucleus and, with or without a caulite con- 

 necting it with the remainder of the neuro- 

 cyte, with a neurite or neurites, performing 

 the one neural function of discharging neural 

 impulses, and with a dendrite or dendrites func- 

 tioning usually as the recipients, sometimes, 

 also, as dischargers of neural impulses. 



F. C. Kenyon. 

 U. S. Department of Agkicultuee, 

 Washington, D. C. 



retinal images and binocular vision. 



In Science of March 11th Professor Stevens 

 added some valuable observations to the facts 

 reported by me in an earlier (February 25th) 

 issue. He has objected to my title ' Binocular 

 Factors in Monocular Vision ' on the ground 

 that "the essential characteristic of binocular 

 vision consists in the simultaneous formation of 

 slightly dissimilar images on the two retinas, 

 with corresponding modification of the per- 

 ception of depth in space." The criticism is 

 more than a merely verbal one and the facts 

 reported assume entirely difierent aspects as the 

 one position or the other is taken. 



It is doubtless true that complete perception 

 of objects depends in large measure on the 

 presence of such slightly different images on 

 the two retinas. But it is also true that even 

 in such cases of complete perception there are 

 sensation factors derived from the movements 

 of both the external muscles of the eyes and 

 the internal ciliary muscles. When the retinal 

 image of one eye is withdrawn, does it follow 

 that these other factors are also withdrawn? 

 Evidently not. On the contrary, there is good 

 reason to believe that so-called monocular 

 vision is complicated by the presence of muscle- 

 sensations from the closed eye. The first 

 question to be raised and answered, then, is the 

 question of the character of the movements 

 which are the sources of these sensations. 

 This was the question taken up in the first 

 paper. Its results were applied directly to the 

 solution of the main problem, namely, what 

 are the binociilar factors in so-called monocular 

 vision? The double images, which are, as 

 Professor Stevens very properly points out, 

 monocular phenomena, were made use of in 

 this experiment merely for the purpose of dis- 



