352 JOHN BEARD, 



On Plate 26, Fig. 79 several ganglion- and nerve-forming cells 

 from this series, as well as one from another, are sketched. They 

 will not be described now, as their consideration belongs more prop- 

 erly to another stage of the paper. 



In embryo No. 157 the transient system is well developed, and 

 numerous sub-epiblastic nerves are present. Only two figures from 

 the series are to be found in the plates (Plate 22 , Fig. 21 , and 

 Plate 24, Fig. 45). 



Fig. 21 affords one of those instances, where of two transient nerves 

 one may be a simple spun fibril, while the other may have one or 

 more ganglion-cells applied to it. 



To the left in Fig. 21 the former condition of a simple fibril is 

 presented to us, while to the right the apparently corresponding nerve 

 has no fewer than seven transient ganglion-cells of various sizes ap- 

 plied to it. Another example, almost exactly similar, was noticed in 

 a section further along in the same series. 



Among the reconstructed figures sketched for the present con- 

 tribution one of the most remarkable is Fig. 45, Plate 24. This was 

 put together from three consecutive sections. The reader may kindly 

 bear in mind that at present we are dealing with facts, or what after 

 repeated examination of the same sections and verification appear to 

 me to be facts. For purposes of symmetry a ganglion-cell (gl.c^) has 

 not been drawn in the myotome of each side, the two actually are 

 present in the myotomes in the positions assigned to them in the 

 figure. It is significant that this should be so, but it is one of those 

 little trifles about the transient apparatus pointing to a former higher 

 organisation and better symmetry of the transient system than it now 

 presents to our incredulous vision. This is a matter which would call 

 for further discussion, and at this point the statement may not be 

 uncalled tor that, taken as a whole, even in Raja, the system would 

 appear to be no longer in the prime of its quondam condition at any 

 stage of the individual development. 



Reverting to the figure (Fig. 45), the two ganglion-cells, one in 

 each myotome, have been commented upon. Then, there are the cen- 

 tral ganglion-cells on the spinal cord, and from these on each side 

 there passes a sub-epiblastic nerve (s.n). As in previous cases the 

 two nerves are of course filled in only as far as they were actually 

 followed. They are not so simple as some ot those on Plate 23. The 

 one to the right has applied to it a ganglion-cell, lying near the tip 

 of the myotome and connected with the centre by means of its own 



