On Some Points in the Development of Petromyzon fluviatilis.1

Abstract

ABSTRACT The development of the Lamprey has occupied the attention of many embryologists during the last fifty years. Of these we owe the most complete accounts of the changes through which the egg passes to Max Schultze, Owsjannikow, Calberla, Scott, Balfour, and Dohrn. I have recently worked through the development of Petromyzon again, and worked out the origin of several organs which have hitherto been incompletely known. In many of the most important points my researches confirm those of the earlier observers, and to these I have only referred at such length as would make the account intelligible ; in others, such as the persistence of the blastopore, the origin of the ventral mesoblast, &c., I differ from previous descriptions ; and some points, such as the development of the heart, of the parts of the brain and cranial nerves, are worked out for the first time.