ZOOLOGY AND BOTANY. MICROSCOPY, ETC. 167 



laying gives rise to two points of gastrulation instead of one. Polj- 

 embrjony in the armadillo is probably due to delayed implantation of 

 the blastocyst in the wall of the uterus. The stop here is not due to a 

 temperature change, since none has occurred, but is very probably due 

 to an exhaustion of the original oxygen supply derived from the ovarian 

 lilood. The degree of duplicity in double individuals depends on the 

 original distance apart of the embryonic buds on the blastoderm. The 

 degree of deformity in the small component of two varies directly with 

 the extent of difference in size between tlie two components. As the 

 large component reaches adult size the lesser component may be repre- 

 sented by a nodular mass or by a twin inclusion. The*primary action 

 of all factors inducing deformity is to inhibit the rate of development. 

 Both monstra in defectu and monstra in escessu may exist in the same 

 specimen, being due to a common cause. Species may be lost by 

 failure to find environments in which harmonious development is 

 possible, but birds and mammals have partially succeeded in controlling 

 their own developmental environment. But in no sense is the regula- 

 tion constantly perfect, and this fact is the underlying cause of frequent 

 malformations and monstrous productions. J. A. T. 



Influence of Parental Alcoholism.— E: C. MacDowell {Proc. Soc. 

 Exper.Biol and Med., IDIO, 16, 125-6). Training records of the off- 

 spring and grand-offspring of a pair of rats heavily alcoholized daily for 

 two months before the birth of the young. Habit formatipn was tested 

 on a Watson maze and a Yerkes multiple choice apparatus. The 

 criteria were the average time per trial, the number of '• perfect " trials, 

 the number of wrong turns or errors. The rats that received alcohol 

 and then- unalcoholized descendants were less successful than the con- 

 trols in meeting the situations presented. J. A. T. 



&• Histolog-y. 



Fibrillar Reticulum of the Human Spleen. — G. Dubreuil 

 {Comptes Rendus Soc. Biol, 1920, 83, 1098-1100). There is a fibrillar 

 reticiihtm throughout the spleen,* except in certain Malpighian cor- 

 puscles. It is seen in the white pulp in the form of collagenous, pre- 

 collagenous and elastic fibres. It is seen in the red pulp in the form of 

 precollagenous fibres in the strands jof Billroth and of ill-diflferentiated 

 elastic fibres round the special endothelium of the venous sinuses. This 

 fine supporting reticulum is attached to the capsule and to the fibrous 

 framework of the spleen. It is useful to distinguish this fibrillar 

 reticulum from the cellular reticulum which forms narrow meshes 

 enclosing free elements. J. A. T. 



Islets of Langerhans and Blood-formation. — M. Aron {Comptes 

 Rendus Soc. Biol, 1920, 83, 1119-22). The hasmatopoietic islets of 

 the pancreas seen in a few mammals result from the transformation of 

 some of their elements into red blood corpuscles. This transformation 

 is cytologically identical with what occurs in the case of the " cellules 

 troubles " of the pancreas in the embryo pig. J. A. T. 



