542 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Neurofibrillar Theory.* — C. K. .Mills Lokls that the elementary 

 fibrils in which is stored neural energy not only conduct or transmit 

 nervous impulses, but by means of the special manner in which they 

 are arrange 1 in the nerve-centres as well as in the periphery, determine 

 the intensity and character of the discharge. The fibrillar coils and 

 bundles are regarded as representing a complicated induction apparatus. 

 Localisation of function is brought about by means of special arrange- 

 ments of intracellular and intercellular neurofibrillary coils and plexuses 

 in the particular regions called centres. As only an abstract of the 

 paper is before us, we have no means of appreciating the evidence on 

 which these conclusions are based. 



Minute Structure of the Muscle-Fibril. t—E. A. Schafer refers to 

 previous investigations in which he showed that the sarcous elements 

 or principal discs of the fibrils of the wing-muscles of insects are tra- 

 versed by longitudinal pores. He brought forward evidence that the 

 process of contraction of the fibril is accompanied by a transference of 

 (fluid?) isotropous substance into the anisotropous disc or tarcous 

 element He has recently found in a leg-muscle fibre of Harpalus 

 runeortus a good object for demonstrating the porous structure of the 

 sarcous elements, and he re-affirms his conviction as to the existence of 

 fine longitudinal pores in the anisotropous substance, into which the 

 isotropous fluid may pass during contraction. 



Muscularisation of Capillary Vessels.^: — S. Mayer gives in an 

 interesting paper a statement of the evidence which has led him to 

 the conclusion that there are smooth muscle-cells on the walls of the 

 capillary vessels. 



Caeca of Birds. § — C. Calleja gives a preliminary account of his 

 researches on the structure of the cascal appendages in birds. He 

 describes four layers. — connective, muscular, lymphatic, and epithelial. 



c. General. 



Concept of Species.f! — K. Mobius says that we are bound to a double 

 outlook on Nature, (a) when we perceive its infinitely rich varietv and 

 heterogeneity, (b) when we perceive it as a harmonious universe. * The 

 second outlook lea<ls the naturalist to group organisms, to detect re- 

 current characters transmitted from parents to offspring, and the concept 

 of species results. 



Our concepts of species are necessarily imperfect inductions ; no one 

 can verify them exhaustively. They are necessarily affected by the 

 naturalist's personal equation ; what are true species to one may not 

 appear so to another. Nature has no ill-defined and well-defined species, 

 but naturalists have. 



Species are only logical unities, quite abstract ; they do not chai ge 

 or adapt themselves ; only the individuals do so. Indeed, the formation 

 of species-concepts is quite independent of questions as to the origin of 

 the real organisms. 



* Pr< c. Nat Sci. Philad.. 1902, p. 113. 



t Anat. Anzeig.. xxi. (1902) pp. 474-7 (4 figs.). J Tom. cit . pp. 442-55. 



§ Boll. Soc. Espan. Hist. Nat., ii. (1902) pp. 250-2 (I fig.). 

 <B. Ges. Nat. Freun.Je Berlin. 1901, pp. 267-9. 



