234 SCIENCE PROGRESS 



tions on a series of 641 normal eggs in a close succession of 

 stages, probably a more complete set than has been dealt with 

 in any other animal. They include stages from the ovarian 

 and tubal egg through maturation, cleavage blastocyst forma- 

 tion, entoderm formation, and the bilaminar stage, to the first 

 proliferation of mesoderm. Entoderm appears almost as 

 early as in the eutheria from mother cells of a unique type 

 that differentiate in one-half of the blastocyst wall. A number 

 of interesting features are described, and the whole is well 

 illustrated. " Studies on the Ovary of the Spermophile 

 (Spermophilus citellus tridecemlineatus), with Special Reference 

 to the Corpus Luteum," have been placed on record by Drips 

 (Amer. Journ. Anat., vol. xxv, March 191 9). This is an account 

 of the activities of the reproductive organs of the animal dur- 

 ing the period of functional activity, particularly emphasising 

 the histological changes in the corpus luteum. Three stages 

 are recognised : the stage of the formation of secretory granules, 

 lasting through most of the period of pregnancy ; the stage of 

 formation of lipoid droplets ; and the stage of regression. 

 Various experiments in ovariectomy, transplantation, etc., are 

 also described, and their import discussed. Jordan describes 

 " The Histogenesis of Blood-platelets in the Yolk-sac of the 

 Pig Embryo " {Anat. Rec, vol. xv, Feb. 1919)- They arise 

 from the giant-cells mainly, but also from the hemoblasts, either 

 by the segmentation of the pseudopodia or by the fragmenta- 

 tion of the larger areas of protoplasm. A similar mode of 

 origin is encountered in both the yolk-sac and the red marrow 

 of bones, and fortunately the absence of metachromatic granules 

 from the osteoclasts enables them to be readily distinguished 

 from the giant-cells. 



Other papers include : 



Allen, " Application of the Marchi Method to the Study of the Radix Mesen- 

 cephalica Trigemini in the Guinea-pig" {Journ. Comp. Neur., vol. xxx, Feb. 1919) ; 

 Chapman, " A Study of the Correlation of the Pelvic Structure, and the Habits 

 of Certain Burrowing Mammals" {Amer. Journ. Anat., vol. xxv, 1919); Ellis, 

 " A Preliminary Quantitative Study of the Purkinje Cells in Normal, Subnormal, 

 and Senescent Human Cerebella, with Some Notes on Functional Localisation " 

 {Journ. Comp. Neur., vol. xxx, Feb. 1919) ; Hanson, "Nerve Foramina in the Pig 

 Scapula : a Peculiar Relation existing between the Dorsalis Branch of Several 

 Spinal Nerves and the Superscapula in the Pig" {Anat. Rec, vol. xv, Jan. 1919) ; 

 Hunt, " The Variations of the Inferior Thyroid Vein of the Domestic Cat " {ibid., 

 vol. xvi, March 1919) ; Mcjunkin, "The Origin of the Phagocytic Mononuclear 

 Cells of the Peripheral Blood" {Amer. Journ. Anat., vol. xxv, Jan. 1919); Pohl- 



