Januaey 10, 1896.] 



SCIENCE. 



59 



servations (sublimate-acetic) and Boveri's 

 (picro-acetic) diifer both from eacb other 

 and from the speaker's. The whole sub- 

 ject, therefore, requires further study with 

 special reference to the technique. 



The following paper by Prof T. H. Mor- 

 gan (Bryn Mawr), on the production of 

 artificial archoplasmic centers, was of 

 special interest and led to much discussion. 

 Unfertilized, as well as fertilized, eggs of 

 sea urchins and ascidians, when treated with 

 salt solutions of a certain concentration, 

 become filled with numerous asters which 

 show in many respects a close resemblance 

 to the normal asters of dividing cells, and 

 may contain a body similar to a centrosome. 

 This cannot be due to polyspermy, because 

 the eggs contain but a single nucleus, and 

 for other reasons. Prof. Morgan is inclined 

 to regard the asters as new formations pro- 

 duced by a rearrangement of the protoplasm 

 under abnormal conditions. In a second 

 paper Prof. Morgan described the develop- 

 ment of dwarf larvae from isolated blasto- 

 meres of Amphioxus, with reference to the 

 numerical relations of the cells. Half- 

 larvse and quarter-larvae always possess a 

 number of cells not precisely one-half or 

 one-quarter the normal number of the full 

 sized animal at the same stage but some- 

 what greater, and these partial larvae show 

 a marked tendency, not however fully 

 carried out, to use the same number of cells 

 in the formation of their organs as that 

 used by the full sized larva. Thus the 

 notochord is always formed of three cells 

 (in cross-section) in larvae of all sizes. 

 These results show that there is an inher- 

 ited tendency to produce a definite num- 

 ber of cells for the formation of particular 

 organs, irrespective of the total size of the 

 embryo. 



The paper of Prof. Conklin (University 

 of Pennsylvania) , on ' Cell-size and Body- 

 size,' discussed a nearly related question 

 from a difierent point of view. Observa- 



tions on the marine gasteropod, Crepidula, 

 show that adult animals vary enormously in 

 size, the dwarfs having in some cases not 

 more than ^\ the volume of the giants. The 

 eggs are, however, always of the same size 

 and are proportional in number to the size 

 of the adult. Microscopical study of the 

 tissues shows that the same is true of the 

 tissue cells. Measurements of cells from 

 various tissues, representing derivatives of 

 all the germ layers (ectodermal epithelia, 

 kidney cells, liver cells, alimentary epithelia, 

 etc.), show that they are not perceptibly 

 smaller in the dwarfs than in the giants. 

 Prof Conklin, therefore, concludes that 

 body size is not dependent on cell size, but 

 on the total number of cells, a result which 

 agrees with that reached by botanists, but 

 differs somewhat from that obtained through 

 a study of the nervous system in higher 

 animals. His conclusion agrees only in a 

 measure with Moi'gan's results on Amphi- 

 oxus ; for the latter indicate that the number 

 of cells in dwarfs, while considerably less 

 than in those of normal individuals, is not 

 strictly proportional to the body size. 



Dr. Lillie (University of Michigan) pre- 

 sented the results of a research on the limit 

 of size in the regeneration of Stentor. These 

 animals, like eggs, may be shaken into fi-ag- 

 ments of various sizes, among which may be 

 found both nucleated and non-nucleated 

 pieces and also naked nuclear fragments. 

 Only such fragments as contain both cyto- 

 plasm and nuclear substance are capable of 

 regeneration. Complete regeneration may 

 take place in a fragment containing only 

 1-27 the bulk of an entire animal. Smaller 

 fragments cannot regenerate. This result 

 is remarkably near to that of Boveri, who 

 has found that the limit of size in egg frag- 

 m.ents capable of producing a complete 

 larva (in sea urchins) is approximately 

 1-20 the volume of the entire egg. 



The second session was devoted in the 

 main to papers on anatomy and develop- 



