640 JOHN BEARD, 



the description, by detailing the many individual cases from different 

 embryos, recorded in my notes. 



Again accepting the germ-nature of these cells as certain, the 

 reader will, perhaps, be ready to believe, that they may occur almost 

 anywhere in the embryo. There are, indeed, very few places and 

 organs in the trunk and in the head, in which germ- cells have not 

 been encountered. No attempt has been made to enumerate the total 

 in any single embryo. The reasons being 1) that from an early period 

 many of them may show signs of abnormality, i. e., of becoming 

 pathological, as will be detailed later on, 2) because it is often difficult 

 to estimate how many normal resting germ-cells some particular cell 

 may represent, and 3) because there are always some between the 

 germinal layers outside the embryo, and the whole of these could not 

 be taken into account in embryos separated from the yolk-sac, as all 

 mine were. Possibly, nay, almost certainly, there are in early stages 

 still others in the upper part of the yolk-sac itself. 



Raja batis No. 419 (10.5 mm) is very like the preceding embryo 

 in the pictures it yields of the germ-cells. It was also preserved and 

 treated in the same way. No record of its normally placed germ-cells 

 has been made, but there are many notes of large and small (0.036 

 and 0.02 mm) germ-cells in very varied situations. In the neigh- 

 bourhood of the pericardium there are many such — a find one makes 

 in most, if not in all, skate-embryos of this period. There are several 

 under the epiblast of the pericardial region, and a single one among 

 the cells of the vagus-ganglion near the medulla. In the posterior 

 pericardial region there is one in the epiblast of the yolk-sac near 

 the embryo. Not far from this a single germ-cell and a group of 

 such are encountered under the epiblast outside the embryo. 



Further back in the abdominal region two large ones are present 

 in the somatopleure, as well as many underneath, or in the splanchno- 

 pleure. In Fig. 22 a vagrant germ-cell from this embryo is depicted. 

 It lay just beneath the epiblast and below the segmental duct. 



In Baja batis No. 402 (11 mm), preserved like the foregoing, 

 the number of germ-cells in normal positions was counted as 177. 

 Those in other places, more especially the large ones of nearly 0.04 mm, 

 are fairly numerous. They begin sporadically in the head-region, 

 where there are two (query — the products of a mitosis?) to the 

 inner side of the third head-somite. Two others are near the fourth 

 ventricle in the mesoblast. 



From my notes it may once more be gathered, that there are 



