ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 707 



Development of Myocardium.* — T. Kurkiewicz has studied this in 

 chick embryos. The formative material arises from the splanchuopleure 

 of the cranial part of the embryo. The cells form at first two 

 '•myocardial pouches " invaginated into the coeloni beneath the gut. 

 The median walls are in contact and form a partition. 



In the cavities of the myocardial pouches the endocardial primordium 

 is paired on to the eight-myomere stage. By the sinking down of 

 the myocardial partition the endocardial primordia are able to unite 

 into a single tube. 



The part of the splanchuopleure which becomes the myocardial 

 primordium is at first a single layer. Two layers are soon established 

 with quite distinct cells. The author traces the gradual differentiation 

 in detail. 



Sympathetic Nervous System of Pig.f — A. Kunz has studied the 

 development of the sympathetic nervous system of the pig, with special 

 attention to the question of the migration of nervous elements from the 

 neural tube along the fibres of the peripheral nerves He finds that 

 medullary cells migrate from the neural tube into the dorsal and ventral 

 nerve-roots in embryos of the pig. These migrating cells are of two 

 types : (1) elongated cells, which are to be regarded as the indifferent 

 cells of Schaper ; (2) pyriform cells, which are to be regarded as the 

 neuroblasts. These migrating cells seem to have their origin in more 

 or less definite regions in the neural tube. Both the indifferent cells 

 and the neuroblasts wander peripherally, and may be traced along the 

 spinal nerves and visceral rami into the primordia of the sympathetic 

 ganglia. The neuroblasts, which migrate from the neural tube into the 

 primordia of the sympathetic ganglia, develop into sympathetic neurones. 

 Thus there is established a direct genetic relation between the sympa- 

 thetic and the central nervous system. A large majority of the 

 elongated cells which wander out from the neural tube and sensory 

 ganglia probably enter into the formation of the neurolemma. 



Regulation in Shell-Making.:}: — Raymond Pearl describes a cast 

 in which the first egg laid by a pullet was very abnormal (elongated 

 ovate pyriform) in shape. In the subsequent eggs laid there was a pro- 

 gressive change of shape. This change was of a regulatory character, 

 the eggs finally coming to be normal in shape. It is shown that this 

 progressive regulatory change follows a logarithmic curve, and the 

 significance of this fact is discussed. The data obtained in this case are 

 held to warrant the conclusion that the shape of the egg is determined 

 by the muscular activity of the walls of the uterus. 



Formation of Shell on Birds' Eggs.§— R. Pearl and F. M. Surface 

 have made a series of experimental investigations with a view to deter- 

 mining the nature of the stimulus which causes the shell to be formed 

 on a hen's egg. They performed an operation on hens as a result of 



* Bull. Int. Acad. Sci. Cracovie, No. 6(1909) pp. 148-91 (3 pis.). 

 f Anat. Record, iii. (1909) pp. 458-65 (2 figs.), 

 t Journ. Exp. Zool., vi. (1909) pp. 339-59 (1 pi.). 

 § Science, n.s. xxix. (1909) pp. 428-29. 



