10 GENEEAL HISTORY OF THE INFUSOEIA. 



fronds of some Desmidiese, e.g. of DocicUum and of Closterium. The vesicles 

 in question are known as the '' terminal globules," or chambers, and would 

 appear to be actually invested with a membrane, and therefore distinct en- 

 closed sacs. In Closterium rostratum and C. setaceum, the collection of moving 

 granules is at a distance from the extremities, and apparently not contained 

 •within a vesicle. In all species exhibiting terminal globules these structures 

 appear in their earliest stage, but disappear when they are dried. 



Ehrenberg imagined the supposed retractile locomotive organs to be fixed 

 to these globules, and that the granular movement within them was no other 

 than that of the bases of these organs. Mr. Varley described the chambers 

 as having contractile walls, and the molecules as transparent spheroids mea- 

 suring from l-20,000th to l-40,000th of an inch, sometimes escaping from 

 their chamber and circulating vaguely and irregularly between the periphery 

 of the gelatinous body and the sheU, Mr. EaLfs regarded the terminal glo- 

 bules to be pecuHar to the Closterina ; yet their contained granules seemed to 

 him '^ to differ in no respect, except in position and iminterrupted motion, 

 from other granules in the same frond." He once saw the motion continue 

 after their escape from the cell. Mr. Osborne (oj>. cit. p. 235) behoves the 

 granules to be cihaiy bodies. He writes : "At the extremities of the green 

 matter there are certain bodies acting with a ciharj- movement within what 

 has been called a chamber, lying towards the point of the membranous sac ; 

 certain bodies, apparently of the same kind, separate from the endochrome in 

 a small mass, appearing at the extreme end of this so-called chamber, or at 

 the side close to the end ; these also impart a ciliaiy movement to the water 

 within the sac around them." He adds (p. 239) : " When the endochrome 

 is of a rich dark green, I find the chamber at the extremity very plain and 

 defined, with its cilia veiy active .... As the endochrome gets of a hghter 

 colour. . . .the chamber becomes smaller and the ciha are barely seen." At 

 p. 236, Mr. Osborne fiu'ther states, " The loose bodies seen in the chamber of 

 Closterium Lunula have very generally cilia, and are, I behove, zoospores ; 

 loose pieces of endochi^ome are sometimes brought round in the current, but 

 these are easily distinguished. I have never seen anything like true cyclosis, 

 i. e. molecules in circular movement, within the so-called chamber." 



Of the purpose of the moving granules vrithin the tenninal globules, the 

 prevaihng notion is that they are zoospores. Meyen hkened them to the 

 " spennatic animalcules of plants ;" and, as above noted, Mr. Ralfs saw them 

 move about as do the zoospores of other Algae when freed from the enclosing 

 capsule and frond. So far as we can gather from his remarks, Mr. Osborne 

 also inclines to this opinion, which is likewise supported by Mrs. Thomas 

 (T. M. S. 1853, p. 37). 



We are sony that we can present no more definite views concerning the 

 nature, characters, and purpose of the terminal globules than those comprised 

 in the foregoing extracts. We find no similar globules in other Algae, and 

 therefore obtain no guide from analogy ; indeed such structures seem to be 

 peculiar to the elongated Desmidieae — to the genera Closterium, Penium, and 

 Docidium ; we must consequently look to subsequent research to elucidate the 

 question. (See Appendix at end.) 



Another sort of internal movement, more prevalent among the Desmidieae 

 than that last considered, is " the sivarming motion" so called, seen either at 

 one or two parts of the frond when mature, or other^dse throughout its con- 

 tents. Having once commenced, it never ceases, but extends itself, and 

 induces changes in the nature, appearance, and colour of the endochi'ome ; 

 for this loses its grass-green colour, acquires the autumnal yellowish or 

 reddish-broTNTi tint, and a finely granular aspect. When the granules burst 



