1884.] 



MICROSCOPICAL JOURNAL. 



77 



placed upon the sputum thus pre- 

 jiarcd, and allowed to remain from 

 three to five minutes. The slide is 

 now washed thoroughly with distilled 

 water, to remove the excess of fuchsin, 

 and the stained spotum completely 

 decolorized by means of a saturated 

 solution of oxalic acid. It is again 

 thoroughly washed in distilled water, 

 after the decolorization, and allowed 

 to dry ; it is now ready to be mounted 

 in glycerin or balsam for examination. 

 With a power of five hundred or six 

 hundred diameters the bacilli will 

 appear as brilliant red rods, no stain- 

 ing of the back-ground being neces- 

 sary. 



One chief advantage claimed over 

 other methods is that in the latter the 

 decolorizing agent employed is dilute 

 nitric acid ; but this, besides being 

 disagreeable to handle because of its 

 corrosive and staining properties, is 

 apt to remove the color from the 

 bacilli too unless great care is taken. 

 Oxalic acid, however, seems to leave 

 the dye untouched in them. 



Sense of Color of Daphnia. — 

 Much has been written of late by va- 

 rious authors on the color-sense of 

 the lower animals, but the subject is 

 still very imperfectly investigated. 

 Some late experiments by Meresch- 

 kowski, on the color-sense of the 

 daphnia, are of considerable interest. 

 Sir John Lubbock has shown that 

 these animals are sensitive to ultra- 

 violet rays which the human eye can- 

 not perceive. The former observer, 

 however, finds that the daphnias are 

 not attracted by the color of a light, 

 but by its brightness. This question 

 has again been taken up by Sir John 

 Lubbock, who has reached a difterent 

 conclusion after numerous experi- 

 ments. He found that if a spectrum 

 be thrown upon a porcelain trough 

 containing daphnias, so arranged that 

 the light on both sides of a given line 

 was equal, the animals showed a de- 

 cided preference for the green over 

 the red end of the spectium. Light- 



ing one-half of a trough with green 

 or yellow light, while the rest was 

 uncolored, the animals preferred the 

 colored light. In another trough they 

 were found to be attracted to a part 

 more brightly lighted than the rest. 

 It seems proved, therefore, that they 

 prefer green or yellow to white light. 

 In other experiments they were found 

 to prefer white light to blue or red. 



Spring Collections. — The ponds 

 are already swarming with infusoria, 

 and fresh growths of alga; are rapidly 

 springing forth. It is the most enjoy- 

 able season of the year for pond col- 

 lecting. We have not yet been able 

 to go out ourselves for a dip in the 

 waters around Washington, but a few 

 days spent in Baltimore enabled us to 

 enjoy a few hours looking over some 

 collections made by that enthusiastic 

 collector Mr. A. D. Balen, who has 

 the happy faculty of always finding 

 something worthy of study wherever 

 he goes. Fortunately for us, Mr. 

 Balen, who had also been visiting 

 Baltimore, left some bottles where we 

 were able to examine them at leisure. 

 Among the numerous infusoria the 

 beautiful rotifers were abundant, and 

 there are few organisms that are more 

 attractive to the eye than these. 



What most engaged our attention, 

 however, was the algjE, which were 

 abundant and of many kinds. Among 

 them we found some fine desmids, 

 which are often in great numbers 

 early in the spring. Attached to 

 some of the plants were numerous 

 jelly-like masses, about as large as the 

 head of a pin. These were found to 

 be balls enclosing a bright-green 

 branching algie, known as Chceto- 

 phora. Ulothrix is sure to be found 

 in almost all early spring collections. 

 It is a slender filament with the cells 

 about as long as broad, filled with 

 green endochrome. Larger filaments, 

 with cells much longer in proportion 

 to their width, are likely to be Mes- 

 ocarpus or CEdogonium ; the latter is 

 readily distinguished by a series of very 



