April 4, 1902 ] 



SCIENCE. 



627 



In the first breaking down of the sperm 

 head a number of chromatin vesicles are 

 formed equal to the number of chromosomes 

 in the sperm. 



The polar bodies are formed about the 

 time the egg enters the glandular portion 

 of the oviduct. They lie between the vitel- 

 line membrane and the cytoplasm. 



In cell division, cytoplasmic currents are 

 present. These currents precede nuclear 

 division, and outline the paths by which 

 the daughter nuclei later migrate apart- 

 They are not confined to the immediate 

 neighborhood of the nuclei, but extend into 

 the region of the future blastomeres. 



The spindles and asters are very minute 

 in comparison with the size of the blasto- 

 meres and the appearance and curved paths 

 of the currents indicate that cytoplasmic 

 division is due to amoeboid movements 

 rather than to the tension of astral fibers. 



Tlie Developvient of Color in the Definitive 



Feather: R. M. Strong. 



The colors of feathers, as was pointed 

 out by Bogdanow ('58), Gadow ('82) and 

 others, are due to the presence of pigment 

 or to special conditions of structure. The 

 pigmentation of the feather takes place in 

 the earlier stages of the development of the 

 feather. The dark brown pigments, com- 

 monly classed as melanins, appear to be 

 formed in the cytoplasm of epithelial cells 

 which are diiferentiated to produce pig- 

 ment. These pigment cells, -or chromato- 

 phores, send out branched processes to 

 those cells which are to form pigmented ele- 

 ments of the future feather. Pigment 

 granules pass from these pigment-cell pi'o- 

 cesses into the cells composing the feather 

 fundament. The formation and the distri- 

 bution of pigment cease before cornifica- 

 tion has proceeded far. There is no redis- 

 tribution of pigment after the feather is 

 fully formed and has burst forth from the 

 sheath enclosing the feather germ. 



A New Type of Hyper-metamorphosis: 

 James G. Needham. 

 This paper will be published in Psyche. 



An Experimental Study of Regulation in 



Stenostoma: C. M. Child. 



When portions are removed from chains 

 of Stenostoma regeneration is complete, 

 provided the piece is not below a certain 

 size. In addition to the regeneration, the 

 piece becomes more slender and narrower, 

 the change first appearing, except under 

 certain conditions, at the posterior end and 

 extending anteriorly until it includes the 

 whole body. The piece does not acquire the 

 same proportions as the original, but 

 approaches them more or less closely. 



To explain this change, it is necessary, 

 first, to examine the methods of locomotion 

 and the locomotor structures of Stenos- 

 toma. The animal, like other rhabdoccels, 

 is covered with cilia which constitute the 

 locomotor organs. 



When undisturbed, Stenostoma shows a 

 strong tendency to attach itself to the sub- 

 stratum. The attachment by the tail, 

 which is used as a sucker, is especially fre- 

 quent and the tail .adheres more closely 

 than any other part of the ventral sur- 

 face. 



Most of the time when the animal is 

 attached the lateral and dorsal cilia are 

 vibrating and are thus acting in opposition 

 to the organs of attachment; the result 

 is the subjection of the body to a 

 certain amount of mechanical tension. 

 That such tension does exist is evident from 

 a large number of observations. 



If we suppose the animal to be attached 

 by the posterior end and the lateral and 

 dorsal cilia vibrating with equal speed and 

 force, the tension upon the tissue at any 

 cross section of the body will be propor- 

 tional to the number of cilia which are 

 anterior to that cross section, i. e., the ten- 



