340 



SCIENCE. 



[N. S. Vol. XXIII. No. 583. 



is known) may account for the peculiar 

 curve. The second explanation is that the 

 magnesium ion, the sulph-ion and the un- 

 dissociated MgSOi, the proportions of 

 which change with the concentration, have 

 altogether different effects upon the solu- 

 bility of gypsum. 



On Monday afternoon the society visited 

 Audubon Park and the sugar experiment 

 station, where opportunity was given to 

 witness all the processes of sugar-making, 

 from the growing cane to finished sugar. 



On Tuesday morning a special train was 

 chartered on the Louisiana Southern Rail- 

 road to take the party to the Braithwaite 

 Sugar Factory where about one thousand 

 tons of cane are worked up per week. In 

 the afternoon a sugar refinery and the Na- 

 tional Rice Mills were visited. 



Chas. L. Parsons, 

 Secretary of Section C, 

 C. E. Waters, 



Press Secretary. 



SCIENTIFIC BOOKS. 

 The< Organization and Cell-lineage of the 

 Ascidian Egg. By Professor E. G. Conklin, 

 Journal of the Academy of Natural Sci- 

 ences of Philadelphia, Second Series, Vol- 

 ume XIII., Part I., 1905. 

 The work on cell-lineage which produced so 

 large a number of papers a few years ago has 

 very naturally led to the study of the visible 

 organization or differentiation of the egg, not 

 only during cleavage, but in earlier stages. 

 The search for cell homologies has given place 

 in large measure to the search for ' forma- 

 tive substances,' ' morphogenic substances ' or 

 ■* morphoplasmic substances ' as the visible dif- 

 ferentiations of the egg have been variously 

 called. And since it is true in biology as 

 elsewhere — perhaps more so — that ' they that 

 seek shall find,' our knowledge of the visible 

 differentiations of the egg-substance is rapidly 

 increasing. 



The paper under review constitutes an im- 

 portant contribution to this subject. It is an 



exceedingly careful study, based primarily 

 upon the egg of Cynthia (Styela) partita 

 Stimpson, with comparative observations on 

 the eggs of Ciona intestinalis (L.) Flemming 

 and Molgula manhattensis Verrill. 



The titles of the seven sections, which with 

 the introduction compose the paper, indicate 

 its scope: I., 'The Ovarian Egg'; II., 'Ma- 

 turation and Fertilization ' ; III., ' Orientation 

 of Egg and Embryo ' ; IV., ' Cell-Lineage ' ;, 

 v., ' Later Development ' ; VI., ' Comparisons 

 with Amphiosus and Amphibia ' ; VII., ' The 

 Organization of the Egg.' 



The most important cytologieal observa- 

 tions concern the character of the spindles in 

 maturation and the first two cleavages. The 

 maturation spindles are without centrosomes 

 and are formed wholly within the nuclear 

 area : at first their fibers radiate in all direc- 

 tions, but finally form a barrel-shaped spindle. 

 Influence of centrosomes and traction of 

 spindle fibers are not concerned in the separa- 

 tion of the chromosomes in the maturation 

 divisions. ^ In the first cleavages a small 

 nuclear spindle similar to the maturation 

 spindles lies between two large asters. 



The spermatozoon enters near the lower 

 pole and rotates after entering. The centro- 

 some is derived from the middle piece and 

 gives rise to the cleavage centrosomes. As 

 regards orientation of the ascidian egg much 

 difference of opinion has existed. Conklin 

 reviews the various systems of orientation, 

 viz., those of Van Beneden and Julin, Seeliger, 

 Samassa and Castle, and gives what appears 

 to be convincing evidence in favor of the first 

 mentioned. According to this the first cleav- 

 age plane corresponds with the median plane, 

 the spindle being eccentric toward the pos- 

 terior pole. The second cleavage is trans- 

 verse. The intersection of these two planes 

 corresponds with the dorso-ventral axis of the 

 gastrula and the third cleavage separates 

 dorsal from ventral cells. 



The account of cell-lineage is complete to 

 a stage' consisting of 218 cells. Gastrulation 

 begins at about the 112'-cell stage. Develop- 

 ment is remarkably rapid, Cynthia and Ciona 

 attaining the tadpole stage in twelve hours 

 after fertilization and Molgula in eight hours. 



