200 University of California Publications in Zoology |Vou.9 
studies. Extruded eggs undergo marked amoeboid movements 
before fertilization. The larvae have no free-swimming stage, 
and this fact, together with the absence of free medusae, would 
seem to leave the species with little ability to seatter about 
widely. The later development is described somewhat more fully 
than the earlier. The great plasticity of the organism from 
beginning to end of its developmental career is specially noticed, 
particular attention being given to the extent to which the 
differentiation both of larger morphological features and of 
cellular details is more or less dependent upon activities of the 
organism and external conditions. Attention is called to the 
close resemblance between the tentacles and the hold-fasts, or 
frustules, abundantly present on the lower part of the stem in the 
early stages of development. The attractiveness of this species 
for biological study, while strong from the accessibility and size 
of the animals, is made doubly so by the number of further 
inquiries suggested by this initial research. 
An important contribution to the reproductive habits and 
embryonic development of the enteropneusta was made by Dr. 
B. M. Davis (1908). <A fuller account of egg-laying is given for 
the species studied than has been recorded for any other of the 
group. Although not sufficient material was secured to make 
possible anything hke a complete description of the earliest 
stages of development, enough was observed to impress the 
author with the resemblance of the embryo in the stages studied 
to the corresponding stages of Amphiorus. This species is the 
second enteropneust known in which no true tornaria stage 
oceurs. By far the most important contribution made by Dr. 
Davis to the development of the group was the conclusion 
reached, on very strong evidence, that the middle and posterior 
body-eavities arise entirely differently from the way in which 
they are currently supposed to arise. He found them to originate 
by backward growth of and constriction from the first, or anterior 
cavity, and not by separate outpocketings from the enteron. 
While there is not sufficient ground in all the germane 
phenomena for attaching as much theoretical importance to the 
particular question of fact here involved, as was done some 
years ago, the matter is nevertheless one of real interest and it 
