78 LECTURE VI. 



analogous to that stage in the generation of tlie Chlamydomonas, 

 whicli is represented at page 24. Jig. 14. 



There is a close and interesting analogy between the above phe- 

 nomena, which were published in 1841, and some of those communi- 

 cated by Dr. M. Barry, to the Royal Society, in January 1841, and 

 published in the Philosophical Transactions of the same year. The 

 clear central nucleus of the blood corpuscle is there shown to form 

 two discs *, which give origin to two cells. We may, likewise, discern 

 in the pellucid nucleus of the yolk, dividing and giving origin to two 

 yolk-cells, according to the German author, the hyaline nucleus of 

 Dr. M. Barry, whose important properties and changes have been 

 so ably elucidated and generalised by that accomplished and patient 

 observer. 



Dr. Bagge traces and illustrates the subsequent divisions of the yolk 

 in the ova of the Entozoa, through the four, eight {Jig- 40.), and 

 sixteen fold divisions, until the number of yolklets {Jig. 41.), like 

 those of the young of the Paramecium in Ehrenberg's experiment, 

 becomes incalculable. A division of the hyaline nucleus has doubt- 

 less preceded the formation of each of these divisions ; and the sub- 

 divided yolk granules have clustered themselves around their respective 

 centres like the working bees around their royal parent. Thus the 

 subdivisions of the yolk decreasing in size as they augment in number 

 the vitelline matter is at length, by the reiterated processes of de- 

 velopment, liquefaction and assimilation of nucleated cells, sufficiently 

 subdivided and refined, and each subdivision or cell, by the con- 

 comitant partition of the hyaline, has become adequately vitalised, 

 to be capable of its further metamorphosis into the appropriate tissue 

 of the embryo worm. 



The minutely subdivided mass is now observed to present a 

 lateral indentation ; and, as this deepens, it assumes the form of 

 a short thick cylinder, bent upon itself (Jig. 42.). By the length- 

 ening and attenuation of the cylindrical mass, the bend assumes 

 the character of a coil (^^. 43.); and now something like an in- 

 tegument, containing a fine granular tissue, may be discerned. 

 Further elongation, attenuation, more complicated coiling, and a 

 greater clearness of the tissues of the embryo worm make its 

 character plainly manifest, and the alimentary canal can be dis- 

 tinguished from the integument, both having been formed, by the 

 subdivision and metamorphosis of the primitive cells {Jig. 44.). The 

 young animal thus built up, now begins to move briskly within the 



* Sec Pliilos. Trans. 1841. PI. xviii. fig. 37. 



