792 BEPORT— 1892. 



planata, Dugfes), whicli is the only one I have not personally studied, is recorded 

 on the strength of a recent memoir. 



There remains the genus Allurns, which is readily distinguished hy its square 

 tail and semi-aquatic habit. Its male pores also are on the thirteenth segment, 

 and there are only two or three species at present known to science. Of these, the 

 Square Tail {A. tetrcedrus, Savigny), the Quadrangular {A. tetraijonurus, Friend), 

 and the Golden Woi-m {A. Jiavus, Friend) are indigenous, and there are also some 

 interesting varieties. 



The generic differences are best understood by presenting the main features in 

 the form of a chart which was exhibited to the Section, and a complete list of all 

 the species at present known to occur in Great Britain is given in the paper. 



A wide field for research is opened up by the study of earthworms. 

 Their distribution, numbers, and utility ; the height to which they ascend, the 

 habitats they prefer, the parasites by which they are infested, the freaks and 

 abnormalities to which they are liable, are only a few of the many topics which may 

 be profitably studied, and concerning which I have for some years past been busily 

 accumulating a mass of interesting material. 



16. The Suman Body as a Conductor of Electricity. 

 Bij H. Newman Lawrence. 



17. Fertilisation of the Eggs of the SticMehack. 

 By Professor J. B. Haycraft. 



18. On the Canalisation of Cells and the Continuity of Living Matter in 

 Plants and Animals. By Dr. Louis Olivier, Editor of the ' Bevue 

 generale des Sciences pures et appliquees.' 



1. We have long known that both in animals and plants certain cells, instead 

 of being completely closed, present in their walls pores which establish a communi- 

 cation between the cellular cavities. These cases have been especially observed in 

 organisms of a lower type (as, for instance, in the Siphonocladacese Algte), which 

 form, as it were, a connecting link between uni-cellular and multi-cellular forms. 

 In the latter, however, special groups of cells have been described, which com- 

 municate by their extremities. Such, for instance, are the sieve tubes of the liber 

 discovered by Hartig, the endosperm cells of certain monocotyledons observed by 

 Tangl, the cells of the pulvinus of the petiole of the sensitive plant and other 

 tissues specially described by Gardiner, &c. 



These instances of cellular canalisation were considered till recent years as 

 exceptional in the tissues of living organisms, where they seemed to be of strictly 

 local occurrence; so that the cell in the higher animals and plants was still looked 

 on as a completely closed chamber; the cavity either containing or free from pro- 

 toplasm could only have osmotic communication with its fellows. 



2. In 1885 I was led to suspect that this theory was erroneous, and to 

 recognise even in highly differentiated tissues and in highly organised individuals 

 the canalisation of the cell-wall and the free passage of protoplasm through the 

 narrow pores. 



On photographing under special conditions three sections of various tissues, 

 artificially stained, I was surprised to see on the plates a very remarkable arrange- 

 ment in the cell-walls, which direct observation had failed to reveal. I attributed 

 this result to the fact that optical and chemical conditions in photography are in 

 various respects different from those in direct vision, and I believed it possible to 

 base on this observation a method of research supplementary to simple microscopical 

 examination. The proofs I have obtained confirm this anticipation. 



I 



