240 abstracts: biology 



differ greatly in coarseness but have the common distinguishing char- 

 acteristic of extreme irregularity of grain. They commonly form long, 

 narrow lenses lying parallel with the foliation of the schists. The asso- 

 ciated foliated rocks, which are of unknown age, are in part of igneous 

 and in part of sedimentary origin. The granite and pegmatite are min- 

 eralogically similar and numerous observed transitions from one into the 

 other, show that the two are in a broad way contemporaneous and are 

 genetically related. 



The pegmatite deposits are essentially coarse granites, their principal 

 light-colored constituents being potash and soda feldspars, quartz, 

 and muscovite, and their principal dark-colored constituents biotite 

 and black tourmaline. Accessory constituents present in almost all 

 pegmatites are garnet, magnetite, and green opaque beryl. Acces- 

 sory minerals present only in certain pegmatites number over fifty 

 species, the most important probably being lepidolite, emblygonite, 

 spodumene, tourmaline, beryl, topaz, and rose or amethystine quartz. 

 Variations through increase in the sodium and lithium content are 

 responsible for most of the gem deposits of the State. 



External conditions, though locally having some slight influence, 

 are not primarily the cause of the pegmatitic textures. The presence 

 of the rarer elements also seems to have had only a minor influence on 

 the texture. Theoretical considerations and the presence of miarolitic 

 cavities in certain pegmatites point to the presence of gaseous constit- 

 uents in the magmas, especially water vapor, as the primary cause of 

 their textures. 



There are many facts which suggest that the difference in average 

 composition between the granite pegmatites and the normal granites 

 was relatively slight and that the pegmatite magmas were not so dif- 

 ferent in physical characters from the granite magmas as has been com- 

 monly supposed. 



The theory that the graphic intergrowths in pegmatites represent 

 eutectic mixtures can not be regarded as proved. 



Field relations suggest that the large areas characterized by partic- 

 ular abundance of pegmatite intrusions correspond to the roofs of granite 

 batholiths. E. S. B. 



BIOLOGY. — Development of sponges from dissociated tissue cells. H. 



V. Wilson. Bulletin U. S. Bureau of Fisheries, 29: 1-30, pi. i-v. 



1911. 



Sponges were cut into small pieces and strained thru fine bolting cloth 



into a dish containing water. The cells settle to the bottom as a fine 



