490 DAVENPORT HOOKER 
even distilled water, which alters the environment of the spinal 
cord. Fischel (14) notes the occurrence of multiple canals in 
well developed salamander larvae after stab wounds in the cord. 
In spite of the general unanimity of opinion that very slight 
stimuli will produce multiple canales centrales, no cases have 
been found in the course of these experiments. The possibilities 
for abnormal development were, in the nature of the case, great. 
In some embryos the two cut ends of the spinal cord were mark- 
edly displaced laterally. Nevertheless, the process of restoration 
of the cord proceeded in the same manner as in those with more 
perfect alignment and the central canal did not reduplicate. The 
cause for multiple canalis centralis formation .thus seems to be 
dependent on other conditions than mere injury to the cord. 
The relationship between the behavior of these frog embryos 
.and the state of the anatomical connections between the ends 
of the severed: spinal cord is of interest, especially in reference to 
the recent work of Coghill (09, 713 and ’14) and of Herrick and 
Coghill (15). These investigators have carefully analyzed the 
reflex mechanism of Amblystoma and have demonstrated the 
developmental correlation between the nervous connections and 
the behavior of embryos of this animal. They have found that 
the sensory-motor connection is first established by the ven- 
tral commissures of the upper portion of the spinal cord and the 
lower portion of the medulla. Thus a stimulus applied to one 
side of the embryo will find its first motor expression in the myo- 
tomes of the opposite side. This crossed reflex are requires, 
for the first swimming movements of Amblystoma, a complete 
and continuous chain of motor and sensory neurones connected 
with one another only at the anterior end of the embryo. 
The experiments show that only on fulfilment of these require- 
ments does the operated frog embryo become completely codrdi- 
nated. This is in the stage 7 days after operation. But this is 
not the first stage in which these frog embryos swim. Four 
days after operation, the motor tracts are connected but the 
sensory are not, nevertheless the embryos swim in a very nearly 
normal manner. It is conceivable, in terms of the reflex mechan- 
