476 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [22] 



fjiMionil i)revioiis to iini)regiiatioii, luul, for many years, received the 

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

 to the l)eli.f that it did not wholly disappear. The latter view is the 

 one now generally accepted by embryologists and rests upon several 

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

 est care. Notwithstanding this some very eminent investigators still 

 hold to their belief in the total disajjpearance of the inuileus of the 

 OAiim, and they base upon this supposed fact a very weighty argument 

 for their favorite hypothesis, which demands that all eggs daring their 

 development shall pass througli the moneron 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 generalizati<m prop- 

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

 overstepped 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 monenda stage of animal development 

 is not yet demonstrated. 



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

 ceUula c cellida true, but that the truth of omnis nHcleus e nucleo is nearly 

 equally well established. The chaotic monera and ursclileim of the 

 Haeckelians ape justifiable only if they carry do grievous errors and 

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

 such i)oints 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 of Clepsine. t Modern histology, that 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 struct- 

 ureless cells «levoid of nuclei or nuclear matter. In fact. In addition to 

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

 that we have proof of the exceedingly complex metamorphosis of nuclei 

 in the nu)st ordinary i)r()cesses of growth. The dividing line between 

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

 enibryonic and embryogenetic develoi)ment 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 i)erson to at 

 least suspend judgment for the present. 



Kecent investigations upon the impregnation of the eggs of the lani- 

 ])rey {Fetromyzon) by Kuplier and JJeuecke show that there are two 

 polar cells extruded from the germ ; one is formed previous to, the other 



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

 Published in French in the Revue Internaiiouale dea Sciences Bioloy'tques, IV, No. 'A, 

 1881. 



t Quarterly Journal of Microscopical Science, July, 1878. 



