640 The American Naturalist. [August, 
After diseussing these, Klaatsch passes to the bony fin-rays 
of the Teleosts and then to their scales, giving details which 
our space will not allow us to repeat, but in each case he comes 
back to the conclusion that in each and every case the so- 
called mesodermal element is of ectodermal origin. Then a 
few instances are taken from other groups—Salamandra and 
Lepus. In the Batrachia he finds the same conditions as in 
sharks and Teleosts. In the Mammals he fails to trace the 
history of his scleroblasts, but he finds here, as elsewhere, pro- 
liferations of ectodermal cells into the subadjacent tissues, 
which, it is possible, may later form the skeletogenous cells. 
It needs hardly be said that these various contributions thus 
superficially summarized are most important, since, if they be 
confirmed, they will tend to an overthrow of many ideas long 
believed to be firmly grounded. The questions concerned are 
far from settled, but we venture to predict that the subject will 
occupy a prominent place in the morphological literature of 
the immediate future. 
LITERATURE CITED. 
’92. N. Goronowitsch. Die axiale und laterale Kopf- 
metamerie der Vogelembryonen. Anat. Anzeiger, VII. 
'98. Untersuchungen über die Entwickelung der sog. Gang- 
lienleisten der Vogelembryonen. Morph. Jahrbuch., XX. 
'92*. Weiteres über die ectodermale Entstehung von Skelet- 
anlagen im Kopf der Wirbelthiern. Morph. Jahrb., XX. 
'88. N. Kastschenko. Zur Entwicklungsgeschichte der 
Selachierembryo. Anat. Anz., iii. 
'94. H. Klaatsch. Uber die Herkunft der Scleroblasten. 
Morph. Jahrb., XXI. 
'93. Julia B. Platt. Ectodermie Origin of the Cartilages 
ofthe Head. Anat. Anz., VIII 
"93". Ontogenetic Differentiations of the Ectoderm of Nec- 
turus. Anat. Anz., IX. 
