20 PROFESSOR P. MARTIN DUNCAN. 



consisting of carbon, oxygen, hydrogen, and nitrogen, with 

 other elements, — such matter as is absorbed by animals and 

 by entities which have irritability and powers of motion, but 

 whose position in the sub-kingdoms is uncertain. That 

 there is abundance of such soluble matter not yet resolved 

 into its ultimate elements, floating in the sea, no one can 

 deny. Wyville Thomson found it deep in the Atlantic, and 

 every excreting marine animal and plant contributes some of 

 it. Evanescent it probably is, but its amount must be 

 enormous. 



Whilst thinking over such heresies as these, some other and 

 contingent probabilities suggested themselves. For instance, 

 if the dark coloured Fuci absorb this organic solution — animal- 

 like — do any amoebiform motions accompany the assimilation? 

 and what is the cell-growth like ? It is hopeless to manipu- 

 late the superficial cells of Fucus vesiculosus with a view to 

 examine into their method of growth and assimilation ; but 

 the so-called " conceptacles" on the clavate ends of the 

 fronds, which contain both round oogonia, and a vast number 

 of extremely delicate finger-shaped processes composed of a 

 succession of cells, yield admirable examples. 



Each hollow enclosed by the frond, or the conceptacle, is 

 full of oogonia, and of the dactylose processes, bathed in a 

 glairy homogeneous viscid colourless fluid. Growth pro- 

 gresses very rapidly in these structures, for the cells are 

 extremely delicate, and it is evidently due to the direct 

 assimilation of the mucus-like fluid which bathes them. 



The following observations were made on a hot and light 

 day in August, upon the growth of the terminal cells of two 

 sets of finger-shaped processes : 



After removing several conjoined processes, and placing 

 them in sea water mixed with the mucus upon a glass slide, 

 due precautions being taken to prevent pressure of the thin 

 glass cover, the relative position of the tops of two processes 

 was carefully noticed and drawn. 



One process (a) had a fine tapering cylindrical terminal 

 cell surmounting a proximal cell (a'). The other process 

 {h) had a short and stout terminal cell, the distal end of 

 which was exactly on a level with the base of the terminal 

 cell of the other process, a. 



Four prolonged examinations of these cells occupied three 

 quarters of an hour, and during that time important amounts 

 of assimilation and growth occurred. 



At the commencement of the observations the condition of 

 cells a and a' (see woodcut, fig. 1) was as follows : 



The terminal cell (a) had a homogeneous thin and very 



