248 



SCIENCE. 



[N. S. Vol. XI. No. 268. 



Uroglena is one of the organisms that has 

 become of interest to engineers and biolo- 

 gists on account of the disagreeable oily or 

 fishy taste and odor imparted by it to water 

 supplies. It is apt to occur in the clearest 

 and purest waters. The Lafayette supply 

 is derived from driven wells in the bed of 

 the Wabash river, and before reaching the 

 reservoir is a most excellent and inoffensive 

 water. This reservoir, however, being un- 

 covered, furnishes an admirable opportunity 

 for the growth of any organism. It seems 

 probable that several small ponds — so-called 

 lakes — that lie within a few hundred feet of 

 the reservoir, serve as culture beds for the 

 Uroglena, and the reservoir may become in- 

 oculated by means of birds and other agents. 

 Uroglena may be found in some one of these 

 ponds at almost any time. The Lafayette 

 reservoir was infested with this organism in 

 the late summer and early fall of 1896, and it 

 has reappeared quite regularly ever since, in 

 the warm weather. The species of Uroglena 

 occurring here corresponds fairly well with 

 U. Americana (Calkins), as described in 

 Massachusetts State Board of Health Re- 

 port, 1891. 



It was not the purpose of the paper to 

 bring out anj^ new facts in regard to the 

 organism Uroglena, but merely to record its 

 rather regular appearance in Lafayette. 



Remarks on a series of wax -models, illustrat- 

 ing cleavage stages in Crepidula. Thomas 

 G. Lee. 



The models shown were made by Mr. 

 B. EricDahlgren, one of I3r. Lee's students, 

 at his laboratory at Minneapolis. Mr. 

 Dahlgren seems especially fitted to do this 

 sort of work, if there is a demand for it. 



Spermatogenesis in Hyhrid pigeons. M. F. 



GUYER. 



Hybrid pigeons exhibit several abnormal- 

 ities in spermatogenesis. These are most 

 marked in the sterile hybrids. In such, the 

 first thing to strike the attention is a curious 



bead-like varicosity about the middle of the 

 spermatozoon head. In the development of 

 such spermatozoa the nucleus does not 

 elongate completely, as it does normally, to 

 form the head ; consequently, at one point 

 there remains a sort of vesicle correspond- 

 ing in position to the original nucleus before 

 the ends pushed out to form the long head. 

 Some of the sterile birds showed also a 

 marked degeneration of the germinal cells. 

 In some cases no spermatozoa were matured 

 and many of the cells had degenerated. 

 Often deeply -staining masses of protoplasm 

 each with a large central vacuole were 

 present. In both sterile and fertile hybrids 

 there was much variation in cell division. 

 Inequalities in chromatin distribution were 

 common and multipolar spindles, abundant. 

 The nuclei of the spermatogonia contained 

 sixteen chromosomes, which is the regular 

 number. In normal primary spermatocytic 

 there are eight large ring chromosomes, 

 each apparently being equivalent to two of 

 the spermatogonial type, but in the hybrids 

 there were oftien more than eight. Some- 

 times there were as high as sixteen small 

 rings, in which case a doubling of the 

 chromosomes had evidently not occurred. 

 When sixteen chromosomes were present in 

 the spermatocytes they were usually located 

 on two spindles, eight to a spindle. Fre- 

 quently both large and small rings were 

 present. These peculiarities in chromo- 

 some formation may point perhaps to a ten- 

 dency in the chromatin of each parent 

 species to retain its individualitj\ If such 

 is the case, then in those cells with two 

 spindles each bearing eight chromosomes, it 

 is evident that after division, some of the 

 new cells will have chromatin from only one 

 of the original parent species and some, from 

 the other. Some of the spermatozoa, there- 

 fore, will bear chromatin from one only of 

 these species. It is a well-known fact that 

 the offspring of hybrids are extremely vari- 

 able, a portion of these variations being 



