THE SMITHSONIAN INSTITUTION. 101 



has been noticed among the lower Pahnellacccr, and in other im]>er- 

 fcctly organized families. Such a mode of multiplying individuals is 

 analogous to the propagation of larger plants by the process of gem- 

 mation, where buds are formed and thrown off to become 'new indi- 

 viduals. When, as in the Lemna or Duckweed, the whole vegetable 

 body is as simple as a phanerogamous plant can well he, the new 

 Irondlets or buds are produced in a manner very strikingly analogous 

 ^to the ])roduction of new fronds in Desmidiace(e. 



The third mode of continuing the species has been observed in many 

 Alg{i3 of the green series, in some of which sporangia are also formed^ 

 bufin others no fructification other than what I am about to describe 

 has been detected. This mode is as follows. In an early stage, the 

 green matter, or endochrome, contained within the cells of these Algaj, 

 is of a nearly homogeneous consistence tliroughout, and semi-fluid ; 

 but at an advanced period it becomes more and more granulated. 

 The granules when formed in the cells at first adhere to the inner sur- 

 face of the membranous wall, but soon detach themselves and float 

 freely in the cell. At first they are of irregular shapes, but they 

 gradually become spheroidal. They then congregate into a dense 

 mass in the centre of the cell, and a movement aptly compared to that 

 of the swarming of bees round their queen begins to take place. One 

 by one these active granules detach themselves from the swarm, and 

 move about in the vacant space of the cell with great vivacity. Con- 

 tinually pushing against the sides of the cell wall, they at length 

 pierce it, and issue from their prison into the surrounding fluid, where 

 their seemingly spontaneous movements are continued for some time. 

 These vivacious granules, or zoospores, as they have been called, at 

 length become fixed to some submerged object, where they soon begin 

 to develop cells, and at length grow into Algaa similar to those from 

 whose cells they issued. 



Their spontaneous movements before and immediately subsequent 

 to emission lead me to speak of the 



MOVEMENTS OF ALGiE 



in general. These are of various kinds, and of greater or less degrees 

 of vivacity. In some Algaj a movement from place to place continues 

 through the life of the individual, while in others, as in the zoospores 

 of which I have just spoken, it is confined to a short period, often to 

 a few hours, in the transition state of the spore, after it escapes from 

 the parent filament, and until it fixes itself and germinates. Many 

 observers have recorded these observations, which are to be found de- 

 tailed in various periodicals.* I shall here notice only a few cases 

 illustrative of the various kinds of movement. The most ordinary of 

 these movements is effected by means of vibratile cilia or hairs, pro- 

 duced by the membrane of the spore, and which, by rapid backward 

 and forward motion, like that of so many microscopic oars, propel the 

 body through the water in different directions, according as the move- 



" See Amalesdes Sciences NiUurelles; Taylor's Ann. Nat. Hist. ; the Linn<ea, Sfc, various Yol- 



umeg. 



