32 SUMMARY OF CURRENT RESEARCHES RELATING TO 



molluscs, and soon ; but the author regards this combination as unjusti- 

 fiable, and prefers simply to speak of a susceptibility to differences of 

 intensity. Again, certain animals respond to light- changes, either by 

 active movements or by a cessation of the usual movements : to such cases 

 the author would apply the term photoJcinetic. Certain burrowing molluscs, 

 for instance, display great activity if entirely exposed to light, but become 

 quiescent if in darkness, e.g. within their burrows. 



Outlines of General Anatomy. * —Prof. Fr. Eeinke has written an 

 introduction to anatomy from a biological basis. He discusses the cell- 

 theory, the life of cells, functional adaptation, regulative processes in 

 growth and regeneration, correlation, and so on, — in short, not anatomy, 

 but the biological prolegomena. 



Segmentation of the Vertebrate Body.f — Prof. Patterson considers 

 that too much stress has been laid upon the occurrence of segmentation 

 in various organs of the Chordata. He believes that it is really a secondary 

 process in vertebrate architecture, and emphasises the number of impor- 

 tant organs which form a longitudinal series, such as notochord, central 

 nervous system, alimentary canal, vascular and genital systems, and are 

 only secondarily and partially affected by the process of segmentation. 

 Even where structures are distinctly segmented, the process is often 

 incomplete, e.g. in regard to the vertebral column. Segmentation is 

 suppressed in the sacrum in most mammals, and in the cervical region in 

 certain Cetacea. In brief, the process of segmentation is superadded 

 to the still more fundamental style of architecture, the longitudinal 

 tubular arrangement of the essential organs of the body. 



Mechanical Theory of Vision4 — Antoine Pizon refers to some of 

 the difficulties which beset the theory that in vision light has a chemical 

 action on the retinal purple with which the rods are impregnated. He 

 refers to the absence of the retinal purple in Invertebrates and in the 

 fovea lutea of Vertebrates, to the absence of both rods and purple in 

 snakes, to the absence of purple in pigeons, bats, and albinos. After 

 prolonged exposure to bright light, the retinal purple is destroyed in 

 frogs, but the animals seem still to see as usual. 



Pizon maintains that the pigment-granules are influenced by the 

 light, not chemically, but so as to exhibit a vibratory movement, which 

 they transmit to the cones or rods with which they find themselves in 

 contact. He refers to Bernard's recent theory, and gives evidence in 

 support of his own, that the phototactic granules move under the influence 

 of light, and transmit their movements to contiguous visual cells. 



Correlation of Colouring in Liver, Skin, and Hairs.§— N. Floresco 

 has previously shown (1) that a snail with a dark shell has a dark 

 mantle and a dark liver ; that a snail with a yellowish-grey shell has an 

 almost transparent mantle and a yellowish liver, and that there are 

 intermediate gradations ; (2) that there is more iron in the livers and 



* Grundziige der allgerueinen Anatomie. Zur Vorbereitung auf das Studium 

 •der Medizin nach biologiscben Gesicbtspunkten bearbeitet, Wiesbaden, 1901, xxii. 

 and 339 pp. and 64 figs. 



t Proc. Liverpool Biol. Soc, xv. (published 1901), pp. 3-18. 



% Comptea Rendus, exxxiii. (1901) pp. 835-7. § Tom. cit., pp. 828-30. 



