156 NATURAL HISTORY SOCIETY OP DUBLIN. 



carried on until the same result is attained — that is, until from each 

 Chlamydococcus-like body an eight-celled, in all respects characteristic, 

 perfect Stephanosphsera is produced. I pass by the time required for 

 these processes, as well as the hours of the day or night with which such 

 developmental changes seem, as in other instances, mysteriously asso- 

 ciated. 



It may be well here momentarily to draw attention to an instance of 

 the great similarity which often exists at certain stages of apparently 

 essentially quite distinct organisms, and which occasionally more than 

 ordinarily forces itself upon our attention. 



I have mentioned that, when I first obtained the material, the pre- 

 sence of Gonium pectorale (Ehr.) was indicated by only a very few spe- 

 cimens indeed ; but in about three weeks, in one of my bottles, this 

 organism made its appearance in very considerable numbers, and they 

 were remarkably fine and beautiful examples of this elegant form. In 

 all respects they seemed to me to agree with the beautiful figures and 

 description of Gonium given by Cohn.*- I may remark that these speci- 

 mens seemed to me considerably larger and finer than those one usually 

 meets with, and more intensely green. In the material alluded to, 

 which I possessed, numbers of the Goniuni were to be found in the 

 various stages of self-division figured by Cohn. But likewise a number 

 of the specimens were present, as is often the case, from which some 

 of the constituent cells of the tablets had been removed by some ex- 

 ternal force, or insufficiency of mutual coherence ; and moreover, what 

 appeared to be these isolated cells (or occasionally indeed dislocated in 

 twos or in threes), were not a few of them to be seen actively urging them- 

 selves about in the surrounding water. Now, furthermore, some of the 

 old globes of the Stephanosphaera occurred upon the slide, and some of 

 these showed the primordial cells in the Chlamydomonas-like state, 

 above adverted to, and these vigorously moving up and down within the 

 old, often much collapsed, envelope-cell, while some of these had lost 

 their normal number of eight, some indeed yet retaining only two or 

 three. Now, at this point I was quite unable to distinguish one of these 

 isolated motile bodies disassociated from a Gonium-tablet from an isolated 

 motile body set free from an old Stephanosphaera-globe, both of which, 

 after the emergence of the latter, moved freely about in company ; nor 

 apart from a knowledge of their origin could eitber be distinguished, I 

 think, from so many examples of Chlamydomonas had they been 

 present. 



But from this I do not mean to argue more than a puzzling resem- 

 blance between the two. A single Gonium in the original material 

 would have sufficed to give origin to the multitudes which afterwards 



* " Untersuchungen iiber die Entwickelungsgeschichte der mikroskopischen Algen und 

 Pilze." Kaiser. Leopold. -Carol. Akademie der Naturforscher, Bonn, 1854, pag. 163. 

 T. 18, Fig. 9, 14, 15, 16, 17. 



