388 E. W. MACBRIDE. 
the tube-feet, consequent upon the loss of the locomotor 
function, explains the reduced stone-canal and madreporite, 
though probably their increased sensitiveness has helped in 
developing the nervous system. 
Literature consulted. 
An account of the earliest publications on Echinoderm de- 
velopment is not given here, since a résumé of them will be 
found in the papers I quote; and I hold it to be a waste of 
time to reiterate with each new paper the whole history of the 
growth of our knowledge ab initio. I mention here only 
those authors on whose results I have, so to speak, built, or from 
whom I have found it necessary to differ. Ludwig’s work on 
the anatomy of Asterids (10) laid the foundation of our know- 
ledge of the heemal and perihemal systems ; though, as we have 
seen, many of his ideas about these structures were incorrect. 
Subsequently in treating of Ophiurids (11) he discovered the 
genital rachis. Hamann (7) extended this result, and pointed 
out the ameeboid nature of the primitive germ cells. Then we 
had Ludwig’s great work on the development of Asterina 
gibbosa (12), the first account of the metamorphosis of any 
Echinoderm which had any pretence of completeness, and to 
which I have constant occasion to refer. His account of the 
changes in external form and of the developmeut of the 
calcareous plates can hardly be improved upon. Owing, 
however, to the imperfect methods in vogue at that time he 
failed to penetrate with equal success into the course of the 
internal changes. He saw nothing of the segmentation of the 
celom or of the ring-like growth of the left coelomic vesicle ; 
he saw nothing also of the origin of genital organs, ovoid 
gland, or oral celom. He did not observe the right hydrocele 
or find the origin of the perihzmal spaces. He missed the 
fixed stage, and he does not seem to have had any clear con- 
ception of the relation to each other of the larval and adult 
planes of symmetry. We owe to him, however, the clear 
distinction of pore-canal and stone-caual, and the recognition 
of the fact that the pore-canal is completely independent of the 
