1889.] MICROSCOPICAL JOURNAL. 37 



are also bits of protoplasm which are largely albuminous (note that 

 again), distinguished by their green color. These ' decompose CO 3 , 

 and fix its carbon, by union with the oxygen and hydrogen of water, 

 into starch.' * They are of the utmost importance, therefoi"e laying the 

 foundations on which the various vegetable substances are built ; but 

 there is nothing more to say about them from an optical stand-point 

 than has been said. 



But even these few parts, we are reminded, are not always distin- 

 guishable in the lowest forms. The cellulose wall and the nucleus are 

 sometimes apparently absent, and the inner layer hardly differs from 

 the substance it encloses. This would correspond almost exactly to a 

 naked rhizopod, an amoeba, so far as structure is concerned. And here 

 let me quote some striking words of Huxley on this point. ' It is not 

 necessary,' he says, ' to the morphological unit of the plant that it should 

 be provided with a cell- wall. Certain plants, such as Protococcus, 

 spend longer or shorter periods of their existence in the condition of a 

 mere spheroid of protoplasm. . . . Therefore, just as the nucleus, 

 the primordial utricle, and the central fluid are no essential constituents 

 of the morphological unit of the plant, but represent results of the met- 

 amorphosis, so the cell-wall is equally unessential. . . . The his- 

 tological analysis of animal tissues has led to results ... of pre- 

 cisely the same character. , . . It is certain that in the animal, as 

 in the plant, neither cell-wall nor nucleus are essential constituents of 

 the cell. . . . For the whole living world, then, it l'esults : — that 

 the morphological units — the primary and fundamental form of life — is 

 merely an individual mass of protoplasm, in which no further structure 

 is discernible.' f Another striking point of resemblance between the 

 two kingdoms Carpenter brings to our notice, that certain Protophytes 

 • not only move like animalcules by cilia or flagella, but exhibit the 

 rythmically contracting vacuoles which are specially characteristic of 

 Protozoic organisms.' 



Now the desmids have the outer coat, primordial utricle, and proto- 

 plasm with its chlorophyll corpuscles which are found in the typical 

 cell as commonly understood. They afford a splendid opportunity, 

 therefore, for the study of cell life. It is evident, also, that their struc- 

 ture is almost as simple and easily mastered as that of the rhizopods. 

 There is little to describe. They have no differential parts, I mean, 

 such as. root, stem, branches, leaves, organs of reproduction; there is 

 no nucleus visible in the majority of cases. In Costnarizwi, Euastrum, 

 and other genera, however, there are often large circular masses of 

 granules which Wolle in some cases calls chlorophyll nuclei, in others 

 inflations or protuberances ; and some regard the whole endochrome 

 as a diffused nucleus, the scattered granules of which they term nucleoli. 

 But we may disregard this as still a matter of dispute. Outside and 

 inside, cell-wall and endochrome, these are all we have to study usually. 

 The inside is much the same in general appearance in the different genera ; 

 the outside gives us great variety of shapes, markings, and processes, and 

 sometimes, as in Closterium, seems to be of a siliceous character. Oc- 

 casionally crystals are met with in the interior, and at the period of 

 reproduction the endochrome presents an altered arrangement. In 



* Carpenter. 



t Encyclopaedia Britannica, Article on Biology. 



