Septembek 29, 1911] 



SCIENCE 



413 



five different species belonging to the phanero- 

 branchiata, the oryptobranchiata, the lechrio- 

 donta and the mecodonta. He comes to the 

 following conclusions in answer to the three 

 questions postulated: 



1. Osseous tissue is divisible into two dis- 

 tinct classes, coarse-fibrous and fine-fibrous. 

 Coarse-fibrous bone is the more primitive of 

 the two. It is formed beneath the periosteum 

 from which at first it is not sharply separated, 

 and in ontogenetically and phylogenetically 

 primitive conditions the coarse fiber-bundles 

 are usually interwoven in an irregular man- 

 ner. In highly developed bone the fiber- 

 bundles are more regularly arranged. Some 

 fine-fibrous bone is usually interspersed among 

 the coarse fiber-bundles. Sharpey's fibers are 

 those bundles of coarse-fibrous bony substance 

 which extend inwards perpendicular to the 

 periosteum. The cement substance of the 

 teeth and the substance of the basal plates in 

 placoid organs of selachians are to be classed 

 with coarse-fibrous bone. Fine-fibrous bone is 

 laid down about the loose connective tissue 

 which accompanies the blood vessels which 

 are enclosed in the sub-periosteal bone or 

 which penetrate the endochondrium. It is 

 laid dovm in concentric layers about the 

 spaces in which the blood vessels lie. No 

 coarse fiber-bundles are ever interspersed 

 among these concentric layers. The dentine 

 of placoid organs and of the teeth is of a 

 nature similar to fine-fibrous bone. 



2. Compact bone is composed mainly of fine- 

 fibrous bone and is a far higher type of bone 

 than the primitive coarse-fibrous hone. The 

 vascular canals in bone appeared at first as the 

 chance accompaniment of the periosteal de- 

 velopment of bone. They proved useful for 

 the nutrition of the bone. Their importance 

 became increased when fine-fibrous bone was 

 laid down in concentric layers about their 

 walls and when blood-corpuscle-forming bone- 

 marrow was developed from the loose connect- 

 ive tissue accompanying the blood vessels. 



3. Enchondral ossification represents the 

 spread of the vascular canals from periosteal 

 bone into axial cartilage. Marrow cavities 

 arose through the anastomosis of branched 

 vascular canals and were present even in the 



extinct ancestors of the present amphibians. 

 The marrow cavity first appeared in the shaft, 

 then extended into the epiphyses. The devel- 

 opment in the epiphyses of special marrow 

 cavities by the ingrovrth of blood vessels from 

 the surrounding periosteum represents a rela- 

 tively advanced stage of development. The 

 elements of the carpus and tarsus phylogen- 

 etically long remain cartilaginous. In some 

 of the lower forms there is a slight periosteal 

 ossification of these bones, but this is never 

 extensive and is not found at all in the high- 

 est vertebrates in which the ossification of 

 these bones is purely enchondral. 



From this study of the development of the 

 skeleton of the limbs in urodeles the author 

 is inclined to take the view that the phanero- 

 branchiates, the cryptobranchiates and siredon 

 are derived from the caduoibranchiates. The 

 caducibranchiates, he thinks, are divisible into 

 two groups, of which one, including the des- 

 mognathinse and the plethodontinEe are dis- 

 tinguished from the second group, the sal- 

 amandrinffi and amblystoma opacum, by a 

 lesser development of marrow cavities, the 

 simple structure of the carpal and tarsal 

 bones, and the almost complete absence of fat 

 cells in the bone marrow. 



The monograph, as a whole, represents a 

 careful and satisfactory study of the subject. 

 C. E. Bardeen 



SCIENTIFIC JOUBNALS AND ARTICLES 



The twenty-second volume of the Journal 

 of Morphology is a memorial volume in honor 

 of Charles Otis Whitman. The third part, is- 

 sued on September 20, contains the following 

 articles : 



' ' Some Problems of Ccelenterate Ontogeny, ' ' 

 Charles W. Hargitt. 



' ' Physiological Animal Geography, ' ' Victor E. 

 Shelford. 



"On the Olfactory Organs and the Sense of 

 Smell in Birds," E. M. Strong. 



' ' On the Eegular Seasonal Changes in the Rela- 

 tive Weight of the Central Nervous System of the 

 Leopard Frog, ' ' Henry H. Donaldson. 



' ' The Physiology of Cell-division. IV., The Ac- 

 tion of Salt Solutions followed by Hypertonic Sea- 

 water on Unfertilized Sea-urchin Eggs and the 

 Eole of Membranes in Mitosis, ' ' Ealph S. Lillie. 



