32 PROGRESS OF MICROSCOPICAL SCIENCE. 



more than they do. A mixture of pure orange xanthophyll and xan- 

 thophyll in absolute alcohol treated with hydrochloric acid would, at 

 the most, give only a pale gi'een, whereas fucoxanthine is changed into 

 a splendid blue substance, and subsequently into a sort of claret- 

 coloured, before finally and slowly fading. Though the spectra of 

 fucoxanthine and yellow xanthophyll are essentially different, yet this 

 blue product is the same. It absorbs the whole of the red end of the 

 spectrum, not transmitting even the extreme red ; and on adding an 

 excess of ammonia this absorption is entirely removed, and the colour 

 is changed to a bright yellow. The spectrum then shows a well- 

 marked absorption-band at the violet end of the blue. On adding 

 excess of hydrochloric acid, the original blue colour is restored : and 

 hence this substance has the unusual peculiarity of being made blue 

 by acids and yellow by alkalies. Hitherto I have never met with it 

 in plants themselves. Taking everything into consideration, we must 

 look ujion fucoxanthine as closely related to xanthophyll ; but at the 

 same time the different effect of solvents in raising the absor^jtion- 

 bands, and the greater permanence when exposed to light, may perhaps 

 make it desirable to class it in a subgrouj). The didl olive colour of 

 those Algce in which it occurs so abimdantly (the Melanospermce) is 

 apparently mainly due to it in a free state, not dissolved in any oil. 

 On comparing the spectrum of the light transmitted by a frond in its 

 natural condition with that of the light transmitted by a portion which 

 has been boiled for a short time in water until the colour has changed 

 to green, it may be seen that the absorption due to the fucoxanthine is 

 considerably raised, just as if at that high temperature it were attacked 

 and dissolved by the oil present in the plant." 



The Production of the Macrogonidia in the Genus Hidrodictyon. — 

 Dr. Horatio Wood has recently published a work on the fresh-water 

 AlgaB of America (a book we trust soon to have for review in these 

 columns), from which the editor of ' Grevillea ' gives some lengthy 

 quotations in a recent number of his journal.* The following re- 

 lates especially to the above subject, and is but a small part of 

 the original excerpt: — "The investigation of the jiroduction and 

 development of the macrogonidia, however, has occui)ied considerable 

 of the time devoted by myself to the microscojie, and I have seen 

 large numbers of specimens in almost all the stages of develop- 

 ment. I have never been able to detect, however, any decided motion 

 in the macrogonidia. They are formed in the protoplasmic stratum 

 already alluded to as occupying the outer portion of the interior 

 of the Hydrodictyon cell. The first alteration in this, presaging 

 their formation, is a disaiijiearance of the starch granules, and a 

 loss of the beautiful, transparent green colour. Shortly after this, 

 even before all traces of the starch-grain are gone, there ai)j)ear in the 

 protoplasm numerous bright spots placed at regular intervals ; these 

 are the centres of development, around which the new bodies are to 

 form. As the process goes on, the chlorophyll granules draw more 

 and more closely around these points, and at the same time the mass 

 becomes more and more opaque, dull, and yellowish brown in colour. 

 * Oct. and Nov., 1873. 



I 



