232 SUMMARY OF CURRENT RESEARCHES RELATING TO 



which some refer to the dermis and others to the endoskeleton. In 

 young specimens of Caretta the author found the primordium of the 

 neural plates in the form of a small bony disc situated in the deep layer 

 of the dermis, and independent of the neural spine, with which there is 

 secondary coalescence. J. A. T. 



Neural Folds. — 0. C. Glaser {Science, 191 G, 505). Observations 

 on the development of the Amphibian Cryptohranchus lead the author 

 to conclude that the folding in of the neural tube is in relation with 

 the volume of the constituent cells, which increases with the absorption 

 of water. But the absorption is rather a cause than a symptom of the 

 folding. J. A. T. 



Coracoid of Pig.— F. B. Hanson {Anat. Record, 1919, 16, 197-202, 

 6 figs.). The author finds that the coracoid process is absent in the 

 pig ; that the subcoracoid is present and ossifies from a single centre ; 

 that the subcoracoid is a glenoid-sharing portion, and is the homologue 

 of the like-named structure in man ; that the subcoracoid has all the 

 characteristics of an epiphysis, and may be the epiphysis of the posterior 

 or true coracoid of the lower forms. More generally, " in the Amphibia, 

 Beptilia, Aves, and Monotremes there is a coracoid throughout life from 

 the sternum to the scapula. In the Placental mammals absorption of 

 the coracoidal bar from the middle portion in each direction results 

 in the complete disappearance of the sternal half of the coracoid, the 

 rodents excepted ; while the scapular half of the coracoid does not com- 

 pletely disappear, but is represented by its distal end, the coracoid 

 process. The Ungulates constitute an exception to this, in which the 

 entire coracoid bar disappears, leaving no trace at either end, excepting 

 always its epiphysis incorporated into the glenoid, and known as the 

 subcoracoid." J. A. T. 



Symmetry Reversal and Mirror-imaging in Monstrous Trout. 

 — C. Y. Morrill {Anat. Record, 1919, 16, 2G5-91, 4 pis.). In some 

 two-headed or otherwise duplicate trout the abdominal viscera of one 

 component showed reversed symmetry in some degree. The mirror- 

 imaging was practically perfect in some cases, while in others it was 

 only slightly indicated or irregular. The facts are discussed in coiTela- 

 tion with human monsters. In both fish and human monsters it is 

 always the same component (the left) which exhibits transposition of 

 the viscera. In cases where mirror-imaging occurs, the arrangement 

 of the two sets of organs is always (unless in the famous Siamese 

 twins) the same. The author discusses the theory of the difficult facts. 

 " From the evidence at hand, it seems probable that the primary cause 

 of visceral asymmetry in Vertebrates is to be sought for at the comple- 

 tion of cleavage rather than in the period of cleavage itself," J. A. T. 



Pharyngeal Tonsil and Bursa in Calf. — Ruth Rand Atterbury 

 {Anat. Record, 1919, 16, 251-64, 8 figs.). Emphasis is laid on the fact 

 that the pharyngeal outpocketings in the calf (when present), and in 

 the embryos of pig and man, " are merely mechanical expressions of 

 the growth conditions of the pharyngeal region, arising! in accordance 



