ADDENDA TO BOOKS I. AND II. 569 



this appears to be the only way to avoid great confusion, such as has 

 bep;un to prevail in some parts of Animal Histology. 



[Other work has hitherto prevented the author from resuming his 

 researches on cell-formation in a systematic manner. He therefore gives 

 only a few additional observations in this edition, with a short report of 

 the labours of others.] 



Page 33. line 33., add : 



Mohl asserts that the primordial utricle is the forerunner of the forma- 

 tion of the cellulose cell-wall. I have not been able to satisfy myself of 

 this. I not unfrequently find the cell- contents of young cells wholly ho- 

 mogeneous, and of yellowish colour ; then one or more colourless, spherical 

 or ovate spaces originate, which expand and meet together like the 

 bubbles in froth. On their junction, the more viscid yellowish sub- 

 stance is then seen to move like little currents ; the bubbles gradually 

 coalesce into a cell-cavity ; the viscid fluid becomes the lining, and often 

 circulates for some time longer. I believe, also, that I am justified in 

 considering Mohl's primordial utricle and the circulating fluid to be per- 

 fectly identical. According to this view, the primordial utricle would 

 be so much the more fluid the younger it was, and therefore could not 

 be the often rather tough wall of the cell only just formed. Of course, 

 however, an extremely delicate and not easily isolated layer of the fluid 

 may, in a more solidified condition, form the primordial utricle, and thus 

 the foundation of the cell. 



Page 37., before the History and Criticism. 



Karsten (Botanische Zeitung, 184?8, p. 457, et seq.) is compelled to 

 oppose my observations on the ferment- cells. His chief objection is : 

 " The ferment-cells (which I must have overlooked) exist already in the 

 uninjured fruits, and pass through the filter;" and he then concludes 

 with a very peremptory protest against all future similar assertions. 

 Nevertheless, after a careful repetition of my researches, I still hold 

 provisionally to my opinion. I am quite convinced by my investigations 

 that the utricles well known to me in certain (not in all, e. g. not in the 

 Apple) fruits, the juice of which is capable of fermentation, have nothing 

 at all in common with the ferment-cells I have so often examined ; that 

 the ferment-cells also certainly originate in some fruits, such as the grape, 

 with the others, and quite independently of them, and then multiply so 

 rapidly in the must, that I could not decide that they were not already 

 nascent in the filtered drops ; but that there is certainly an epoch for 

 the grape, in which neither ferment- cells nor those utricles exist, notwith- 

 standing that the juice is capable of fermentation, and developes per- 

 fectly good ferment ; that especially apple-juice, which ferments so well, 

 contains neither those utricles nor ferment-cells ; that, altogether, the 

 juices of all fruits prepared and filtered before the commencement of 

 the formation of ferment-cells are altogether destitute of anything solid, 

 anything organic ; in fact, of any thing visible besides drops of oil. I 

 believe that Karsten would have kept back all his objections, at least for 

 the present, if he had combined the internal development of succulent 

 fruits with his fermentation experiments. These peculiar utricles have 

 to be spoken of at length in another place ( 39. Appendix, 574, c.). 



