526 ROSS G. HARRISON 



Tiginaria, which may be caught in old tree stumps, proved to 

 be the best adapted of those which were obtainable early in the 

 season, and two large specimens wove enough web for all of the 

 experiments with frog tissues. Later the common grass spider, 

 Agalena, was obtained in abundance. This form spins an ex- 

 tremely fine but dense web which is admirably adapted for the 

 purpose. The individual threads of the web are amazingly 

 thin and even under the oil immersion lens they appear as fine 

 lines, the thickness of which can scarcely be measured. 



EXPERIMENTS WITH TISSUES OF THE FROG EMBRYO 



From this material seventy-one cultures were made in all. 

 They are grouped in several series, of which the first two were of 

 a preliminary nature, having been designed to ascertain what 

 fluid media could be used. 



Series I. Only inorganic media were used, as follows : tap 

 water, 0.325 per cent NaCl, Ringer's solution without sugar, 

 Locke's solution half diluted. Solid support was afforded in 

 all cases by spider web. The tissues used were: medullary 

 cord alone, medullary cord with axial mesoderm attached, and 

 ectoderm. Eight preparations showed cell movements. Of the 

 six that gave negative results, three were those which were 

 mounted in tap water; they disintegrated on the second day. 

 Two were in the dilute sodium chloride. One specimen in dilute 

 Locke's solution lived seven days and the others from one to four 

 days. 



Series II. In these experiments both inorganic solutions (Ringer 

 and 0.4 per cent NaCl) and defibrinated serum were used. Thir- 

 teen pieces were supported on web and eight were put up in hang- 

 ing drops. None of the latter showed any movement of cells except 

 one in which the drop touched the bottom of the chamber. In 

 this some cell movement took place on the glass. Only one of 

 the cultures in the sahne solutions on the web g.'^ ve positive indi- 

 cations of movement, the others showing no promise from the 

 beginning. Of the nine in serum five were on web and four 

 unsupported. Four of the former showed active movement, 

 one was evidently injured since histolysis of the tissue began 



