162 HICKS^ ON THE DIAMORPHOSIS OF LYNGBYA, ETC. 



wavy frouds, the cells being held together by colourless 

 intercellular substance. 



5. The formation of gonidia from these fronds, and their 

 segmentation. 



6. The assumption of linear growth by these cells. 



The whole of these changes are so palpable^ can be observed 

 so constantly, and are, at the same time, so simple in their 

 relations to one another, that one can scarcely imagine how 

 they can have been separated, not only into distinct species 

 but into different families of algae. Thus the linear stage is 

 called Lyngbya ; the early stage of collateral segmentation, 

 the Schizogouium •. the adult stage, Prasiola ; while the 

 gonidial growth has been classed under Palmellacese. And 

 this has been done by most algologists. Meyen, indeed, had 

 pointed out a connection between them;"^ but his opinions 

 were denied by Jessen,t and ignored by most others. It is 

 a striking instance of the insuperable tendency of some to 

 look upon every distinct form as a separate species. 



And this tendency has in itself a power of checking further 

 research ; for as it is assumed at starting that a given form 

 has unalterable limits, or only a definite amount of variation, 

 of necessity all other forms exceeding those limits are excluded 

 without compromise, and without inquiry beyond; and 

 hence it is that life-history, and laws of variation, are fre- 

 quently neglected. So easy a plan is it of surmounting the 

 difficulties which necessarily attend such studies, that one 

 perhaps ought not to be astonished at its prevalence ; how- 

 ever, there can be no doubt but that it has tended very much 

 to the confusion now existing in the simpler classes of life. 

 Had the attention hitherto given to the multiplication of 

 species been devoted to the study of the life-changes, the 

 state of our knowledge on such points would have been very 

 different to what it now is. 



That these remarks may not seem out of place, and to 

 show how unphilosophical has been the arrangement of the 

 algse mentioned in the heading of this paper, I adduce the 

 following. 



The characters are stated to be of — 



Lyngbya. — Filaments elongated, simple, distinctly articu- 

 lated (intus laxe annulata, Agardh and Lyngb.) ; with a 

 distinct cellulose tube, giving off gonidia (motionless spores), 

 capable of dividing laterally into a small expansion, by double 

 or quadruple series (Jessen, Meyen). 



* Meyen, ' Liniiffia,' 1827, ii, p. 388. 



f Jessen, 'Prasiolse Monograph Kilife,' 1848, p. 19. 



