Eiogen in the Ovarian Egg. 295 







Art. XXX Y. — On Biogen, or the so-called Albumen in the 

 Ovarian Egg. (From a letter of E. Desor, to Prof. C. Vogt, 

 in Giessen. Communicated by the author for this Journal.) 



Like many embryologists I have often had doubts concerning 

 the real nature of the so-called albumen in the eggs of the in- 

 vertebrate animals. The theory of von Baer, that in animals 

 without oviducts, the albumen is formed in the ovary itself, 

 did not satisfy me, from what I had seen of the metamorphoses 

 of the immature egg. And having an opportunity during the 

 past winter to examine a great number of invertebrate animals, 

 I took the occasion to investigate more closely this supposed 

 albumen. 



The following facts in their general outline were observed in 

 the eggs of various animals, particularly Mollusks and Worms, 

 but most thoroughly in the ovarian eggs of Ascidise. 



On the 15th of May of this year, I first had the opportunity of 

 examining the ovary of Ascidia rasiica from Boston harbor. I 

 extracted the ovary of a full-grown animal, and on bringing it 



under the microscope, I found it filled with vesicles of very vari- 

 ous size and appearance ; some very small and transparent; oth- 

 ers somewhat larger, with granular contents; and others again, 

 the largest of all, having in the middle an opaque ball surrounded 

 by a transparent liquid. " With a stronger magnifying power ( 100 

 diameters) I discovered yet smaller eggs looking not larger than 

 a pin's brad, nnd measuring less than T £*of a millimetre, (fig. 1.) 

 whilst others had the apparent size of a pigeon's egg, (fig. 9.) 

 Between these extremes I found all intermediate sizes, as shown 

 in the following drawings, figures 1 to 9, and satisfied myself that 

 they were all eggs. The smallest consisted apparently of a sim- 

 ple vesicle, (fig. 1.) In somewhat larger ones, two outlines 

 were visible, an outer one, the vitelline membrane, and an inner, 

 the germinative vesicle. Within this 1 saw besides a smaller 

 vesicle, the germinative dot, (fig. 2.) 



As usual, the germinative vesicle in the smallest egg is very 

 large in comparison with the enclosing membrane (the vitelline 

 membrane.) By d rrees the latter enlarges, whilst the former 

 seems to remain stationary. 



Before the ovulum has increased to double the size of the ger- 

 minative vesicle, it is perfectly transparent, (fig. 1-3.) In the 

 < g of fig. 4, the liquid began to be somewhat turbid, and the 

 germinative vesicle seemed as if surrounded by a light cloud. 

 In somewhat larger eggs (fig. 5.) I found the cloud more distinct, 

 particularly about the germinative vesicle ; and with an increased 

 power (500 diameters) 1 could already distinguish very minute 

 granules in it. Th the egg of fig. 6, these granules were distinct 





