193 



(most frequently), or of two germ-cells, replace the aberrant germ-cells 

 of normal embryos. That is to say, they occupy the positions, in 

 which in noraial embryos of Raja germ-cells are met with other than 

 in the germinal nidus. Thus, as examples, megaspheres, each equal 

 to two, four, or occasionally eight germ-cells, are observable in splanch- 

 nopleure, gut-epithelium, epiblast, spinal cord, in the germ-path, and 

 even on the subintestinal vein. Of these megaspheres or large germ- 

 cells 26 are recorded in my table, in addition there are two germ- 

 cells of the normal size, i, e., 0.02 mm. Of all these there is 

 one single germ cell in the normal position, the site of 

 the future germinal nidus! 



As all the others are in abnormal situations, such that as a rule 

 in normal embryos they would there probably degenerate, the em- 

 bryo is practically sterile. 



Parenthetically, it may be remarked, that the very next normal^) 

 skate-embryo (no. 750, 4.5 mm) examined exhibited a remarkable re- 



1) The statement, that this embryo is normal, is quite correct, but 

 it must be qualified. It has been found necessary to work over each 

 embryo at least twice, once under low magnification, and once under the 

 2 mm apochromatic of Zeiss. The statements in the text are based upon 

 an examination under low powers, i. e., under two very fine Haktnack 

 lenses, nos. 4 and 5, now 23 years in my possession. Under the 2 mm 

 apochromatic it has more recently been noted, that many, at any rate, 

 of the megaspheres here were entangled in the network of pluripolar 

 mitosis, and, therefore, in, or on the way to, degeneration. Further 

 particulars maj'- be reserved for subsequent publication. The interest 

 of the point is this, that it probably indicates how an abnormal con- 

 dition of the germ-cells may seriously affect the embryo. The opposite 

 state of affairs obtains in the abnormal embryos, nos. 742 — 747, where 

 pathological conditions in the latter result in abnormalities in the germ- 

 cells. 



Bj^ these finds two probable causes of abortions in early human 

 embryos, for instance, are indicated, viz., deficiency in the embryo, 

 _Jeading to abnormalities in its germ-cells, and abnormalities in the 

 germ-cells rendering the embryo useless. In brief, these may be de- 

 scribed as "embryo abnormal, resulting in disaster to its germ -cells", 

 and "germ -cells pathological, making the embryo useless". Which of 

 these be the commoner, is difficult to say. It may be added, that my 

 friend, Dr. J. A. Mureay, has found what both he and I interpret as 

 pluripolar ^concentric) figures in germ - cells in an aborted pathological 

 twin human embryo of about two months. Both "embryos" were aborted, 

 but the one was apparently normal. Some of these "pluripolar mitoses" 

 were in germ -cells in the germinal nidus, others were free — in the 

 bodj^-cavity! Comment is quite superfluous. 



Anat. Anz. XXI. Aufsätze. 13 



