476 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [221 



general previous to impregnation, bad, for many years, received tbe 

 assent of many distinguished investigators, though not a few still hold 

 to the belief that it did not wholly disappear. The latter view is the 

 oue now generally accepted by embryologists and rests upon several 

 series of investigations carried out by several observers with the great- 

 est care. Notwithstanding this some very eminent investigators still 

 hold to their belief in the total disappearance of the nucleus of the 

 ovum, and they base ui>on this supposed fact a very weighty argument 

 for their fiivorite hypothesis, which demands that all eggs during their 

 development shall pass tlirough the monerou or non-nucleated stage of 

 development, in accordance with the doctrine that the development of 

 the individual must briefly recapitulate the development or evolution 

 in time of the race to which it belongs. This grand generalization prop- 

 erly conceived is truly important, but its more recent defenders have 

 overstei)ped the bounds of legitimate deduction and induction in their 

 efforts to establish a consistent theory of animal evolution, in that later 

 researches have shown that the monerula stage of animal development 

 is not yet demonstrated. 



Latterly it has been affirmed by Strasburger* that not only is omnis 

 cellula e cellula true, but that the truth of omn'm nucleus e nucleo is nearly 

 equally well established. The chaotic monera and urscldeim of the 

 Haeckelians are justifiable only if they carry no grievous errors and 

 mischief into the sacred realm of science. The extensive discussion of 

 such points to the exclusion of the true methods of investigation has 

 called for several digests of the existing state of the facts in the case, 

 one of the best of which is that given by Mr. C. O. Whitman, in his 

 Embryology ofClepsine. + Modern histology, thati is to say, what we 

 have learned to know of cell development within the i)ast decade, dis- 

 countenances most emphatically the doctrine of the existence of s^rwcit- 

 ureless cells devoid of nuclei or nuclear matter. In fact, in addition to 

 the dictum of Strasburger, we owe it largely to Professor Flemmiug 

 that we have proof of the exceedingly complex metamorphosis of nuclei 

 in the most ordinary processes of growth. The dividing line between 

 the phenomena of growth, cell development, and the early phases of 

 embryonic and embryogenetic development is certainly not as easily 

 made out in many cases as might be supposed, and if there were no 

 other argument against themonerula hypothesis, the facts of embryology 

 and histology alone would be sufficient to impel a candid person to at 

 least suspend judgment for the present. 



Recent investigations upon the impregnation of the eggs of the lam- 

 prey {Petromyzon) by Kupffer and Benecke show that there are two 

 l^olar cells extruded from the germ ; one is formed previous to, the other 



* In an address delivered before the congress of German naturalists, at Danzig. 

 Piiblislied in French in the Revue InUrnatlonale des Sciences Biologiques, IV, No. 3, 



1881. 



t Quarterly Journal of Microscopical Science, July, 1878. 



