212 Proceedings of the Royal Physical Society. 



nisli us with a type of tlie morphological arrangement and 

 the physiological relations of vegetable cells alike distinct 

 from this and from the ordinary one. The very deep pits 

 in such thickened cell walls have often led vegetable histo- 

 logists erroneously to imagine their protoplasm continuous ; 

 but the cases above mentioned, however, appear to me to 

 furnish a considerable amount of new evidence in favour of 

 that view ; which, however, while very attractive, especially 

 as serving plausibly to explain many remarkable physiolo- 

 gical phenomena — such, for instance, as the propagation of 

 an impulse through the leaf of Drosera — will require much 

 farther research for its verification. 



13. The question so long debated during the early days of 

 the cell theory as to the nature and respective homologies of 

 such structures as the cellulose wall and primordial utricle of 

 the vegetable cell, the cysts of Amoeba3 or Gregarines, the skele- 

 tons of Diatoms and Thalamophora, etc., the gelatinous invest- 

 ment of many Radiolarians, the matrix of cartilage, sarcol- 

 emma, neurilemma, intercellular substance, etc., still affords 

 room for many detailed inquiries. We remain as yet com- 

 pletely ignorant of the laws of formation of such " organic 

 crystallisations " as the skeletons of Radiolarians and Diatoms, 

 though such siliceous deposits may yet furnish a transition 

 from the chemistry of the carbon compounds to that of the 

 analogous silicon compounds ; or, still better, a glimpse into 

 the play of forces within the protoplasm which produces them. 



Nageli's theory of the growth of starch grains and cell 

 walls by intussusception has recently been vigorously attacked 

 by Schimper,* and I have pointed out that the cell wall in 

 Chlamydomyxa labyrinthuloides is " distinctly formed by the 

 deposition of successive laminre, not by intussusception and 

 subsequent differentiation, an important fact in view of the 

 wide prevalence of the latter and somewhat overstrained 

 theory "f (see fig. 4). The laminated structure of the cel- 



* Bot. Zeit. 1880-81. 



+ Observ. on the Resting-Stage of Chlamydomyxa (Quart. Jour. Micro. Sci., 

 Jan. 1882). See Strasburgcr's recently published work, " Ueb. d. Ban u. 

 Wachsthum d. Zellhiiute," Jena, 1882, in which a vast mass of similar evi- 

 dence i.s adduced. 



