380 



SCIENCE. 



[N. S. Vol. XXI. No. .532. 



A good fixing liquid ouglit to have the 

 following qualities: (1) to produce no dis- 

 locations, (2) rapid penetration, (3) to 

 cause no overhardening, (4) not to impair 

 staining capacity. 



As a fixing liquid for general use which 

 fulfills these requirements I recommend 

 the folloAving mixture: 



Alcohol absol 200 



Water 300 



Glac. acetic acid 90 



Nitric ac. pure cone. . . 10 



Corrosive sublimate... 55 (saturated). 



The objects are put in this liquid for a 

 period of from 6 to 24 hours, then washed 

 in 70 per cent, alcohol with iodine which 

 must be frequently renewed; after this 

 they can be kept indefinitely in 70 per cent, 

 alcohol. 



The Formation and Behavior of the Mi- 

 crozooids of Hceniuiococcus pluvialis: 

 Florence Peebles, Woman's College. 

 Under normal conditions the resting cells 

 of Hcematococcus produce more macro- 

 zooids than microzooids. If, however, the 

 dead leaves and other objects upon which 

 they live are subjected to frequent periods 

 of rapid desiccation the nuriiber of micro- 

 zooids formed is greatly increased. These 

 microzooids can be obtained in large quan- 

 tities if the mother cells are subjected, in 

 the early stages of division, to cold and 

 then suddenly changed to a warm tempera- 

 ture ; or, if kept at first in the dark, and 

 then placed in direct sunlight. They are 

 positively heliotropic and gather in swarms 

 on the side of the vessel that is nearest the 

 light. 



After escaping from the mother cell a 

 mierozooid swims about for twelve to 

 forty-eight hours and then comes to rest, 

 loses its flagella, develops a cell wall and 

 begins to grow. After a day or two, the 

 first cell wall is east off and a new one 

 forms. A large number of microzooids 



have four flagella, others two. These with 

 four have exactly the same shape but are 

 larger than those with two. Many double 

 individuals have been observed, and these 

 after a short time fvise into one normal 

 spore. Although no two microzooids have 

 been found in the first stage of conjugation, 

 it seems highly probable that they are 

 gametes, and that under certain conditions 

 conjugation takes place, and that the zooids 

 with four flagella are zygospores. 



The Evolution of Color-producing Struc- 

 tures in Birds: R. M. Strong, University 

 of Chicago. 



The colors of feathers from between 

 seven and eight hundred birds were 

 studied. The causes of colors in feathers, 

 the nature of color characters and the evo- 

 lution of color in birds were considered. 



The material studied argues strongly in 

 favor of the orthogenetic theory of evolu- 

 tion of color pattern by continuous varia- 

 tion, advocated by Professor Whitman. A 

 great many peculiar modifications in struc- 

 ture and pigmentation occur in birds. 

 Some of these produce color phenomena 

 which often seem, at first, to be unrelated 

 to other colors found in birds. These 

 studies have demonstrated, however, that a 

 perfect continuity exists between color 

 characters. Complete series of intergrad- 

 ing conditions occur in single feathers, at 

 the margins of color areas, and in allied 

 species. 



Extreme developments, like the phenom- 

 enon of iridescence, occur very generally 

 in bird feathers, but often in incipient 

 stages not observable except with the aid 

 of the microscope. Colors involving com- 

 plete differentiations in structiire and pig- 

 mentation sometimes appear in amounts too 

 small to effect the total color impression 

 received by the unaided eye. These color 

 phenomena are ordinarily perceived only 

 when they are produced by a large propor- 



