Jaxuauy Is, 1895.] 



SCIENCE. 



71 



Cope and Scott, who jioiutt'il out that 

 while the term ' honioplasy ' Wcas proposed 

 by Lankaster the phenomenon itself was 

 early pointed out hy Darwin and has 

 been fully elucidated by palaeontolojjists. 



Mr. Seitaro Gato, of the Johns Hopkins 

 University, gave a demonstration of some 

 pai'ts of the P>toi)aiasitic Trematodes in- 

 cluding a number of featui-es fi"om his full 

 memoir upon this subject recently pub- 

 lished in Japan. 



Mr. A. P. Matthews, of Columbia, fol- 

 lowed \\-ith a paper on the Morplwlnykal 

 Changes in the Pancreatic Cell, eorresponcUng 

 ii'ith Functional Acfiriti/. The cells of JVec- 

 tuntg are exceptionally large and favorable 

 for observation of the changes wliich occur 

 before and after feeding. The striated ap- 

 pearance of the outer zone of the pancreatic 

 cell is due to coarse cytoplasmic filaments 

 or threads which end in the centre of 

 masses of chromatin within the nuclear 

 membrane. In fact, these threads are di- 

 rectly continuous with the cytoplasmic reti- 

 culum in the inner zone ; these threads are 

 often coiled and in such cases explain the 

 structures known as Nebenkerne. When 

 the gland is secreting the zymogen granules 

 and reticulum are washed out of the cell by 

 lymph currents and new thread substance 

 is manufactured l)y the chromatin. Dur- 

 ing the so-called ' rest ' of the cell the thread 

 substance degenerates into zymogen gran- 

 ules and the cytoplasmic reticulum of the 

 inner zone. The zymogen granules grow 

 by accretion. The thread substance grows 

 by accretion at the chromatin end. The 

 nucleus undergoes no appreciable changes. 

 There are indications that the ('hromatin is 

 a ferment, and that it is the essential forma- 

 tive element of the cell ; probably tliis is 

 true of all the cells and all chromatin ; if 

 so, the character of cj-toplasm and new 

 chromatin formed will depend on the char- 

 acter of the nutrition. It is po.ssible that 

 the chromatin of embryonic cells differenti- 



ates as a result of dillerentiations depend- 

 ent upon the location in the segmenting cell 

 mass of the chromatin of the original blas- 

 tomeres. If this is true it is unnecessary 

 to assiime that characteristics are repre- 

 sented deiinitely in a so-called ' stirp ' lo- 

 cated in the chromatin. 



Professor J. S. Kingsley, of Tufts College, 

 next i)resented a paper upon the Anatomy 

 and Jielationshi})!' of Pauropida, on behalf of 

 Mr. F. C. Kenyon. 



Professor Aljiheus Hyatt, of the Museum 

 of Comparative Zoologj-, Cambridge, pre- 

 sented a paper summing up his researches 

 upon the ParallcUmis between the Ontogeny and 

 Phytogeny of Pecten. 



Professor Andrews submitted for Profes- 

 sor T. H. Morgan, of Bryn JIawr, some of 

 his observations recentlj' made in Naples at 

 the American table supported bj- the Smith- 

 •sonian Institution. It is found that the 

 unsegmented eggs of a sea-urchin may l)e 

 broken into minute fragments which develop 

 into perfect larva'. One such fragment may 

 be one-fiftieth of the volume of the egg and 

 yet develoj) into a ga.strula if it contain a 

 male and a female pronucleus. The gas- 

 trula thus produced is so exeeedinglj' small 

 that three in a row are no longer than 

 an infusorian, such as Paramoecium. The 

 volume of such a gastrula is one-sixty-fourth 

 part of that of a normal gastrula. While 

 the number of ct-lls in a normal blastula on 

 the point of invaginating is five to seven 

 hundred, the numlier in one of the minute 

 blastulas at the same stage niiiy be as small 

 as sixty. With such facts we explain the 

 known difficulty in rearing larvie fi-om iso- 

 lated cells of late cleavage stages, as due to 

 a limit in the number of cleavages pos.sible 

 before gastrulation. That is, gastrulation 

 comes after a definite number of cleavages 

 and a cell has its possible cleavages reduced 

 in a certain ratio by the number of preced- 

 ing cleavages. 



The paper of Professor F. H. Herrick, of 



