214 



SCIENCE. 



[N. S. Vol. XIX. No. 475. 



aboiit the time of first cleavage in normal 

 fertilization, the rate of development falls 

 gradually behind the normal, being in 

 specific cases as 2:3 at the moment of 

 active swimming, and 1:2 in time of de- 

 velopment of pluteus. The artificial gas- 

 trulffi are less symmetrical and less active 

 than the normal forms. The pluteus three 

 days old, by measurements, equals in size 

 the normal pluteus a day and half old, 

 differing in lack of symmetry and poorly 

 developed skeletal spicules. Mouth, 

 oesophagus and stomach are present, but 

 no anal opening has been noted. Develop- 

 -ment in fused fragments is similar to that 

 of the whole egg, except that no fusions 

 are knoAvn to have become plutei. No 

 membrane appears, but a perivitelline mem- 

 brane surrounds eggs placed in a solution 

 composed of 50 cc. of 2-| n MgCL solution 

 and 50 cc. of sea water for from one to two 

 hours. The same effect, though in not so 

 great a percentage of eggs, is obtained by 

 use of 2^ n NaCl solution in same propor- 

 tions. 



The primary nucleus equals in size and 

 eccentric position in egg (as revealed in 

 sections) the nucleus of ootids measured in 

 sections of the ovary. The nucleus ad- 

 vances to the center, enlarges. A small 

 aster with central dark body (partheno- 

 centrosome) appears in contact with ex- 

 terior of nuclear membrane. This divides 

 to form the amphiaster. The various 

 phases of mitosis ensue. The chromatin 

 nucleolus contributes to formation of chro- 

 mosomes. These are between twelve and 

 fourteen in number. In a few cultures the 

 nucleus was amoeboid in movement and 

 amitotic in division. From such cultures 

 no larval forms developed. Both cleavage 

 asters and cytasters contain central bodies 

 similar to centrosome of fertilization. These 

 bodies appear to be formed de novo, and 

 in the case of the cleavage asters there is 

 evidence which suggests that their origin 



may be in the second polar body. Cy- 

 tasters appear to divide and are some- 

 times centers of cleavage. They are more 

 abundant in ootids placed in the concen- 

 trated solution. Nuclear division is not 

 necessarily followed by cytoplasmic cleav- 

 age. Cleavage of the cytoplasm is pre- 

 ceded by nuclear division. 



"^Biological Interpretation of Skeiu Varia- 

 tion: Frank E. Lutz, University of 

 Chicago. (Read by title.) 

 A departure from the 'normal' curve of 

 biological measures may be brought about 

 either (1) by removal of a number of indi- 

 viduals from one side of the mean, (2) by 

 increase of individuals or (3) a combina- 

 tion of the two. In skewness caused by 

 removal, we have, in the sign of the skew- 

 ness, a prophecy of the direction of varia- 

 tion. In skewness caused by the starting 

 of a new race about a mean within the 

 range of the old race, skcAvness would be 

 prophetic at the beginning of evolution and 

 historic at the end. The distance between 

 the two means is a factor determining the 

 uni- or bi-modality of the combination 

 cui've. Skewness as the result of both addi- 

 tion and removal seems too complicated 

 for present analysis. And in no case have 

 we, at the present time, enough data to 

 interpret definitely, in any particular case, 

 the significance of skew variation. 



The Correlation of Brain Weight with other 

 Characters: Raymond Peakl, University 

 of Michigan. 

 *27ie Relation between the Law of Ances- 

 tral Heredity and Mendelianism: Frank 

 E. Lutz. (Read by title.) 

 The 'purity of the germ' idea applies 

 quite as well to the law of ancestral hered- 

 ity as to Mendelianism and is in harmony 

 with it. The confusion seems to have 

 arisen because of the difficulty in distin- 

 guishing between the different grades of 

 intensity of the characters used in certain 



