Maecii 3, 1899.] 



SCIENCE. 



317 



ita sternum — all died. The average oscilla- 

 tion of variation around an ideal mean was 

 also shown to be almost invariably in excess 

 for the birds which perished, and the con- 

 clusions arrived at were as follows : 



The birds which perished were not simply 

 accidental suiierers from the severity of the 

 storm, but were birds which were phj'sically 

 disqualified for enduring the intensity of the 

 New England climate, as expressed by the 

 storm of February Ist, and they were con- 

 sequently eliminated by natural agents. 

 The result of this elimination produced in 

 this particular locality a colony of birds 

 measurably different from those existing be- 

 fore the storm, that is, the action of natural 

 selection resulted in the elimination of the 

 unfit and the survival of the fit. 



On the Anatomy of the Spermatozoon of In- 

 vertebrates. G. W. Field. (With demon- 

 stration of the apical body.) 

 The widest diversity in the form of the 

 spermatozoon is found among the diiferent 

 groups of the invertebrated animals. Closer 

 examination shows that there is, however, 

 one type of form which obtains in by far 

 the greater majority of species, and that the 

 aberrant forms are peculiar to those species 

 which have either become parasitic, e. g., 

 certain worms and arthropods, or which 

 have acquired specially modified secondary 

 sexual organs, e. g., lobster, crayfish, Lmi- 

 ulus. 



The common type is the familiar tailed 

 form, prevalent one in the groups Ccelen- 

 terata. Vermes, Echinoderma, Mollusca, Ar- 

 thropodaand Tunicata. The three general 

 divisions are usually distinct and readily 

 recognizable Rarely the spermatozoa of 

 all the species studied have a special struc- 

 ture or apical body at the anterior tip of 

 the head. It has been variously described 

 as (1) an adaptation for boring into the 

 ®gg; (2) a remnant of the cytoplasm ; (3) 

 fluid expressed from the nucleus upon 



shrivelling ; (4) a micropore surrounded 

 by ' Ringkorper ; ' (5) an apical button 

 present in the unripe spermatozoon ; (6) 

 the sperm centrosome. The first five opin- 

 ions seem to have little importance when 

 considered in connection with the origin of 

 this apical body. While the opinion of 

 myself and others that it is the sperm cen- 

 trosome is refuted by the weight of evidence 

 that the sperm centrosome comes from the 

 middle piece of the spermatozoon, yet, so far 

 as I know, the function of this apical body 

 has not been noted by any of those who 

 have studied so successfully the fertiliza- 

 tion process. Since it has the same micro- 

 chemical reactions and the same, origin as 

 as the middle piece, it would appear as if 

 its fate must be of considerable consequence. 

 I have found this apical body in more than 

 forty species, representing all the groups 

 from the Coelenterates to Amphioxus (in- 

 cluding Toxopneustes). By others it has 

 been found in upwards of twenty additional 

 species. 



The fact that the apical body is present 

 in the spermatozoon of well-nigh every 

 species studied indicates that it has some 

 very special significance which should not 

 be overlooked by workers on the phenomena 

 of fertilization. 



The Middle Piece of the Urodele Spermato- 

 zoon. J. H. McGregor. (Read by title.) 



Tlie Origin of the Yolk in the Egg of Molgula, 



Henry E. Crampton, Jr. 



The author presented the principal re- 

 sults of an extended study upon the early 

 history of the ascidian oocyte, considered 

 from a chemical as well as from a purely 

 morphological aspect, made by means of 

 carefully controlled aniline staining sup- 

 ported by artificial digestion and other 

 tests. It was found that the cell-body at 

 the beginning of enlargement of the primary 

 oocyte presents no albumen reaction. 

 There is, however, a small albuminous gran- 



