March 12, 1897.] 



SCIENCE. 



423 



be no lack of correspondence in their teach- 

 ings. This trnth is now receiving a signal 

 confirmation by the discoverj' of fossil plants 

 in marine shell-bearing deposits, especially 

 Iq the Lower Cretaceous of Portugal, of 

 Texas, and of California. Neither is the 

 ' botanical time piece ' either too slow or 

 too fast, and the organic pendulum has al- 

 ways swung in perfect unison on both sides 

 of the Atlantic. Lestee F. Ward. 



Washington, D. C. 



THE A3IERICAN MORPHOLOGICAL SOCIETY* 

 Tlie Role of Water in Groioth. C. B. Daven- 

 port. 



In developing tadpoles of various am- 

 phibia the amount of water contained was 

 determined at short intervals between the 

 time of hatching and midsummer. These 

 determinations showed that during the first 

 week or two of development the amount of 

 dry substance in the embrj'o remains nearly 

 absolutely the same as it is in the just- 

 hatched larva, where it constitutes little less 

 than half of the whole weight. During 

 this period the immense increment in 

 weight which accompanies the outlining of 

 the form of the larva and its organs is due 

 almost solely to imbibed water. It is the 

 specific imbibition of water then which de- 

 termines the direction of differential growth 

 in the developing tadpole. As in plants 

 this ' grand period of growth ' is followed 

 by one of histological differentiation, dur- 

 ing which the absolute (and relative) quan- 

 tity of dry substance increases rapidly. 

 The Structure and Function of the Midgut in 

 Terrestrial Isopods. J. P. MoMueeioh. 

 The general result of the study of the Iso- 

 pod midgut may be summed up as follows : 



1. The so-called ' midgut ' of the terres- 

 trial Isopods is of ectodermal origin and is 

 in reality a portion of the proctodaeum. 



2. It is lined by an impervious layer of 

 chitin. 



* Concluded from page 392. 



3. The cells which compose it possess no 

 definite boundaries and form an epithelial 

 syncytium. 



4. The fibrils which traverse the cells from 

 the basement membraue to the layer of 

 chibin are, throughout the greater part of 

 their extent, of the same material as the 

 basement membrane, their central ends, 

 however, being apparently chitinous. They 

 are not protoplasmic, as Ide has maintained. 



5. The nuclei frequently show great ir- 

 regularities of form ; these irregularities are 

 sometimes due to injury, but in other cases 

 appear to be normal and to indicate a power 

 of amoeboid movement. 



6. The conjugation of the nuclei, de- 

 scribed by Eyder and Pennington, does not 

 occur. 



7. Fragmentation of the nuclei occurs as 

 a degenerative change, but amitosis for 

 growth or regeneration, if occuring at all, 

 is infrequent. 



S. The increase in size of the ' midgut ' 

 appears to be due not to an increase of the 

 number, but to an increase of the size, of the 

 cells present at the close of embryonic life. 



9. Feeding experiments indicate that the 

 midgut does not possess an absorptive 

 function ; it merely serves for the passage 

 of undigested material to the exterior. 



A paper giving in detail the evidence on 

 which these conclusions are based is in the 

 hands of the editor of The Journal of 

 Morphology. 



The Result of the Suspension of Natural Selec- 

 tion as Ilhistrated by the Introduced English 

 Sparrow. H. C. Bumpus. 

 Over 1,700 eggs were critically examined, 

 and ' curves of frequency ' were drawn to 

 illustrate the differences between the Euro- 

 pean and American specimens. It was found 

 that the American eggs presented a much 

 greater amplitude of variation than the Eu- 

 ropean, that they were smaller and that 

 they were of a strikingly different shape. 



