lO 



MORPHOLOGY OF THE CELL. 



water. The coalescence gives the impression of a union of two drops of fluid ; but 

 the protoplasm is never a fluid ; and, independently of other circumstances, there is 

 a fact that shows that altogether peculiar forces are here active which are absent from 

 all fluids; — the spiral band of chlorophyll of each of the two conjugating protoplasmic 

 bodies is preserved in the contraction ; it only becomes closely drawn together ; during 



^ 1., 



Fig. S- — Spiro^yra loiigata. Cells oi two filaments preparing for 

 conjugation, they show the spirally coiled bands of chlorophyll in 

 which, at different places, lie wreath-like arrangements of starch- 

 grains ; small drops of oil are also distributed through them (cf. sect. 6) ; 

 this is the behaviour of the chlorophyll after the action of strong sun- 

 light ; the nuclei are also to be seen in the cells, each surrounded by 

 protoplasm, threads of which touch the cell-wall in different places ; 

 a and b are the protuberances preparing for conjugation (X550). 



Fig. 6. — Spirogyra lo7igata. A Cells in the act of conjugation ; at a 

 the protoplasmic body of one cell is passing over into the other; at b 

 this has already taken place ; the band of chlorophyll together with 

 starch-grains is still partially recognisable. B the young zj'gospores 

 surrounded by membrane ; the protoplasmic body contains numerous 

 drops of oil {XS50). 



the coalescence the ends of the two bands of chlorophyll place themselves together in such 

 a manner as to form one band. The conjugated protoplasmic body clothes itself with 

 a cell-wall, and forms the body called a Zygospore, which germinates after a period of 

 repose of some months, and developes a new filament of cells. With greater or smaller 

 deviations from this plan, conjugation takes place in a group of Algge comprising a large 

 number of species, the Conjugatae, among which the Diatoms must be included, and in some 

 Fungi. In the latter more considerable deviations occur {e.g. Syzygites, Mucor stolon'ifer). 

 In Spirogyra nitida it also happens (according to De Bary, Conjugaten, p. 6) that one cell 

 conjugates with two others, and takes up their masses of protoplasm ; in these cases a 

 Zygospore is the product of the contents of three cells. In the IVIyxomycetes the swarm- 

 spores (Myxo-amoebae), which are endowed with a peculiar motion, coalesce gradually in 

 great numbers, and finally form large, motile, membraneless protoplasmic bodies, the 

 Plasmodia, which only at a subsequent period are transformed into numerous cells. 



In the cases hitherto considered, the uniting protoplasmic bodies are of equal 

 size ; the process of fertilisation in many Cryptogams differs only in the fact that 

 the two protoplasmic bodies which coalesce are of unequal size, and otherwise of 

 different properties. In Book II we shall treat in detail of the reproduction of 

 Cryptogams; here we need only state that the male, motile fertilising bodies (Sper- 

 matozoids) of Cryptogams are naked protoplasmic bodies, which are considered 

 to be primordial cells ; in the female organ of these plants is a cell which opens 

 outwardly, and contains a protoplasmic body which is fertilised by the spermatozoids. 

 In cases which have been accurately observed (Oedogonium, Vaucheria), these coalesce 



