572 SUMMARY OF CURRENT RESEARCHES RELATING TO 



When Amphioxus is cut in two, both halves lose much in sensitive- 

 ness, the posterior proportionally much more than the anterior. The 

 anterior part of the nerve-tube is brain-like, the posterior part cord-like. 



The skin contains tactile organs, but there are no derived organs 

 such as lateral line organs or cars. The photoreceptors are the eye-cups 

 of the nerve-tube, and these probably represent the elements from which 

 the rod- and cone-cells of the lateral eyes of Vertebrates have been 

 derived. 



The rod- and cone-cells of the Vertebrate retina are inverted, not 

 because they have retained a morphological position dependent upon an 

 external origin, but because of their orientation, acquired as effective 

 eye-cups in the nerve-tube of a primitive Vertebrate. 



The chemical sense-organs of Anrphioxus are located in the skin, and 

 are chiefly important as organs for testing the character of the chemical 

 environment, rather than for the selection of food. From these un- 

 differentiated chemical sense-organs have probably been derived the 

 organs of taste and smell, of which the former are apparently not present 

 in Amphioxus, while the latter may be represented by the so-called 

 olfactory pit. 



Perforations of Marine Animals.* — W. C. M'Intosh discusses in a 

 highly interesting manner the boring of shells by Cliona, of rocks by 

 sea-urchins, of wood by Ghdura terebrans, Limnoria lignorum, Pholas, 

 Teredo, and the like. He has brought together manv scattered obser- 

 vations, and he discusses impartially the various theories of the mode 

 of perforation. 



Differentiation of Faunas.f — K. Holdhaus discusses the various 

 ways in which an area with homogeneous fauna may be divided into 

 two or more areas with distinctive faunas. (1) An area may be divided, 

 and the originally similar contingents may evolve on different lines, 

 e.g. in the Galapagos islands with their species of Tropidurus, etc. 

 (2) An area may be divided, and some of the constituents in one of the 

 parts may be eliminated, e.g. in the contrast of Elba and Corsica in re- 

 spect of Pselapkm and other small beetles. (8) Different migrants may 

 be added to the two areas. Separation may lie due to geographical 

 isolation by some insuperable physical barrier, or to a diversity of 

 vital conditions. Two faunas may become uniform by migration 

 (resulting in fusion of the indigenous forms and the migrants or in 

 extirpation of the indigenous forms) or by an elimination of the forms 

 which distinguish the two. The author gives examples of the different 

 possibilities. 



Tunicata. 



Japanese Appendicularians.J — T. Aida describes Kowalevshia tenuis 

 Fol., Fritillaria haplostoma Fob, F. pellucida Busch, F. rittcri sp. n., 

 Oilcopleura longicauda Vogt., 0. fusiformis Fob, 0. megastoma sp. n., 

 0. mikrostoma sp. n., 0. comntogastra sp. n., 0. rufescens Fob, 0. dioica 



* Zoologist, Feb. 1908, pp. 1-20. 



t Zool. Anzeig., xxxiii. (1908) pp. 38-45. 



% Journ. Coll. Sci. Univ. Tokyo, xxiii. art. 5 (1907) pp. 1-25 (4 pis.). 



