46 



SCIENCE 



[N. S. Vol. XXVI. No. 654 



acts from being put through them. The ex- 

 periments indicate the presence of mental 

 images. Miss Isabel McCracken, in studying 

 " The Egg-laying Apparatus in the Silkworm 

 {Bomhyx mori) as a Eeflex Apparatus," per- 

 formed various operations on the nervous sys- 

 tem to learn the localization of function in the 

 egg-laying reflexes. The posterior abdominal 

 ganglion is the controlling center and exhibits 

 a high degree of independent activity. ■ The 

 vitality of the silkworm moth, as measured by 

 length of life and capacity of the reproductive 

 system to function, is not impaired by removal 

 of the head. The exact influence upon the 

 Teproductive function of the cerebral, thoracic 

 and the several abdominal ganglia was experi- 

 mentally determined. " A Study of the Cho-. 

 Toid Plexus," by Walter J. Meek, adds con- 

 firmatory evidence to the conclusion that the 

 plexuses are concerned in the secretion of the 

 cerebro-spinal fluid. 



SOCIETIES AND ACADEMIES 



THE ST. LOUIS CHEMICAL SOCIETY 



At the meeting of the St. Louis Chemical 

 Society, held June 10, three papers were pre- 

 sented on the general subject " The Fixation 

 of Atmospheric Nitrogen." 



1. "By Plants," J. Arthur Harris, of the 

 Missouri Botanical Gardens. 



2. " By Direct Oxidation," Carl Hambue- 

 chen. 



3. " As Ammonia and Cyanides," Dr. P. W. 

 Frerichs. 



The speakers presented the general history 

 of the several processes, and the methods em- 

 ployed, together with an account of the present 

 status of the subject. Dr. P. W. Frerichs 

 concluded that even if the Chilean sources of 

 combined nitrogen should be exhausted within 

 twenty-five years, and even if the low nitrogen 

 content of mineral coal (about 2 per cent.) 

 excluded this as a source of combined nitro- 

 gen, except in the few cases in which this 

 nitrogen can be obtained as a by-product, still, 

 chemistry will be quite able to supply all the 

 combined nitrogen that shall be required. 



C. J. BORGMEYER, 



Corresponding Secretary 



DISCUSSION AND CORRESPONDENCE 



DR. Eastman's recent papers on the kinship 



OF the arthrodires' 



Every one who labors with the time- 

 honored problem of vertebrate descent must 

 consider, sooner or later, the arthrodiran 

 " fishes," for these, with forms similar but even 

 more puzzling, were the most conspicuous and 

 diversified of earliest chordates. They are 

 first known in the upper Silurian, run their 

 gamut of evolutional prosperity in the middle 

 Devonian, and become extinct in the early 

 Carboniferous: the earlier forms were small 

 with tubercle-like teeth, the later, often of 

 considerable size, with many types of denti- 

 tion, tubercular, trenchant, or crushing. Un- 

 happily, however, the various forms of 

 arthrodires are known only imperfectly, and 

 the fact that various writers have considered 

 them as related to almost every and widely 

 separated groups of living fishes is enough to 

 indicate how little is known of their anatomy. 



Among the latest contributions to this un- 

 satisfactory theme are three papers by Dr. C. 

 E. Eastman, and these contain such reaction- 

 ary views as to the kinship of arthrodires 

 that they merit a somewhat extended review. 

 For, in the matter of vertebrate descent, there 

 should, I think, be entered a friendly protest 

 against Eastman's conclusions — all the more 

 necessary on account of his deservedly high 

 authority in matters of palseichthyology — and 

 the reasons should be summarized for regard- 

 ing his arguments inadequate. On the other 

 hand, I do not believe that this is the place to 

 support in detail a rival theory— it is rather 

 to show the intricacy of the materials in- 

 volved and the limitations to which our con- 

 clusions must be subject. 



Eastman brings out in his papers three 

 essential theses. He aims to demonstrate : (1) 

 That arthrodires are specialized lung-fishes, 

 principally on the evidence of dental plates and 



* " Dipnoan Affinities of Arthrodires," Am. 

 Jour. Sci., Vol. XXI., February, 1906. " Structure 

 and Relations of Mylostoma," Bull. Mils. Comp. 

 Zool, Vol. L., No. I., pp. 1-34, pla. 1-5, May, 1906. 

 " Mylostomid Dentition," ibid., Vol. L., No. 7, pp. 

 211-229, 1 pi., February, 1907. 



I 



