CHRONIZOOSPORES OP HYDRODICTYON. 107 



those of T^'jdrodictyon and Pediastrum, which proceed from 

 the transformation of the micro-zoospores ; the second group 

 ■will contain the chroni-spores of Coelastrum and other allied 

 forms -which at no period enjoy any freedom of motion. 



Interrupted development and absence of motile power are 

 not therefore necessarily true external characters of the fruit 

 of sexual reproduction in the algce ; we must also admit new 

 exceptions to the generally received rule that the motionless 

 spores^ or hypnospores [Rukesporin) must be considered in all 

 cases as zoospores. 



Further researches on the presence of zoospores in other 

 families of Hydrodidyon, and their replacement by immotile 

 chroni-sporesj will no doubt permit us one day to separate in 

 a satisfactory manner, the hypnospores which belong to a 

 sexual reproduction from those which are formed without 

 previous foundation. Precise observations made from this 

 point of view must lead to the recognition of other zoospores 

 in many algte, besides those which germinate immediately, 

 which have hitherto been confounded with the latter, but 

 which do not germinate until they have undergone a definite 

 period of immotility or rest {Daner gust and). The mode of 

 existence of a vast many species of the genus Protococcus, as 

 yet so vaguely and imperfectly known allows us easily to 

 suppose that many of them are only zoospores of other algse 

 in a state of rest, or clu'oni-spores. It is even probable that 

 the chronizoospores of Hydrodictyon may have been taken 

 for a sort of Protococcus and described as such ; nevertheless 

 the distinguishing characters given to the protruded species 

 of these plants are necessarily so insufficient, that it is 

 impossible to affirm anything about thera.^'=" 



In summing up all that phycologists have written on the 

 spores of algTC, many observations occur tending to indicate 

 the existence of chronizoospores clse-wiiere than in the Hydro- 

 dictyea. 



The hypnospores of Chlanydococcus phivialis, which at once 

 suggest themselves, I believe must be understood quite dif- 

 ferently ; they do not arise from the direct transformation of 

 the truncated and active reproductive bodies vrhieh are called 

 zoospores though they are, in reality, each of them, a perfect 

 plant, endowed with motile power [Schocemunde P flange) ; but 

 are engendered in the plastic contents of these same bodies, 

 and the circumstance of their being born solitary and not 

 several together renders their generation exteriorily a pheno- 

 menon always analogous to the transformation of the chroni- 



* Fide, with reference to this. Dr. Hicks' papers in this Journal. 

 VOL. II. — NEW SER. H 



