OF THE INVERTEBRATE ANIMALS. 11 



membrane which has just been condensed, and which closely 

 surrounds it; if we denominate the oil-globule the germinal 

 spot, the vesicle thus formed corresponds to the germinal vesicle. 

 If we place a solid body in a fluid filled with suspended mole- 

 cules, the latter are rapidly deposited upon it ; this phasnome- 

 non can be readily observed in any liquid in which we suspend 

 a little powdered chalk or wood, and immerse a piece of chalk or 

 wood. We find similar molecules in the tubules of the ovary, 

 but they are innumerable, and consist of oil-globules surrounded 

 with condensed albuminous coatings. When these are depo- 

 sited around the newly-formed germinal vesicle, we have the 

 yolk, which, after the deposition of the fatty molecules present, 

 is surrounded by new albuminous layers, the vitelline membrane 

 and chorion, just as a ciystal in a saline solution. 



I consider that the formation of the ovum-cell as such may be 

 arranged among known physico-chemical processes, but it does 

 not then possess vitality ; the totality of the motor phaenomena, 

 which we call life, results primarily from that peculi.ar combina- 

 tion of the above-mentioned with new masses and forces which 

 are in motion, by the addition of a new system of the same kind, 

 — the spermatic fluid in impregnation. 



Lastly, if we study the yellowish masses on both sides of the 

 siliceous carapace in the gelatinous envelope of Frustulia salina, 

 which were pointed out by Ehrenberg as ovaries, we find the 

 interesting circumstance, that elementary analysis aids us when 

 our present optical resources (magnifying 1200 diameters !) cai-ry 

 us no further, i. e. that with the assistance of the former we can 

 ascertain the physiological nature of organs, the isolation and 

 further anatomical tracing of which would be impossible even to 

 an Ehrenberg, with his wonderful skill in the vivisection of 

 microscopic objects. Thus these yellowish masses are in reaUty 

 only fat ; they disappear on treatment with aether ; and the 

 latter contains considerable masses of a brownish fat in solution. 

 The whole process of solution can be directly traced under the 

 microscope in such specimens as have been previously placed in 

 alcohol to remove the water. If we observe in the same manner 

 the action of potash, we see that the remaining mass (proteine 

 substance, probably the foot observed by Ehrenberg), which fills 

 the siliceous carapace, dissolves, whilst the yellow masses con- 

 tinue to run together, assuming a spherical aspect, and finally 

 issuing from the apertures of the siliceous carapace in the form 



