104 J. T. CUNNINGHAM. 



represent the appearance of eggs and sections of eggs with 

 considerable accuracy, but he interprets them as leading to 

 the conclusion that the vitelline elements are derived from 

 the nucleus, a conclusion which I hold to be entirely erroneous. 

 I will proceed now to a detailed description of the develop- 

 ment of the yolk in the various species which I have examined. 

 I will deal first with — 



Pelagic Eggs containing one or more Oil Globules. 



In the same family of fishes, some species may be charac- 

 terised by eggs with oil globules, others by eggs in which 

 these structures are absent. In the Pleuronectidseit is curious 

 to note that all the left-sided species have a single oil globule 

 in the egg, namely, the turbot and brill (Rhombus), the 

 megrim (Lepidorhombus megastoma), and the topknot 

 (Zeugopterus). The soles, which are right-sided, produce 

 eggs in which there are numerous small oil globules, and in 

 the remaining right- sided species forming the genera Pleuro- 

 nectes, Hippoglossus and Hippoglossoides, the eggs are 

 without oil globules. In the family Gadidse a similar state of 

 things occurs, in certain genera, e. g. Molva, the ling, an oil 

 globule being present in the eggs, while in the genus 

 Gad us it is absent. 



In immature specimens of the brill examined during the 

 spawning season, the scattered globules are seen in the 

 larger eggs. These oil globules first appear in contiguity 

 to the membrane of the germinal vesicle. Fig. 6 shows the 

 appearance of a portion of the ovary of a specimen of this 

 species 12| inches long, examined at Grimsby on May 30th, 

 1895. The same condition was observed in a number of 

 specimens examined on this date ; they were from lOf to 12| 

 inches long, and captured near the German coast off the Sylt 

 Island. A piece of one of these ovaries was preserved in a 

 mixture of picro-sulphuric acid and spirit, and in sections of it 

 stained with Mayer's carmalum the oil globules, or the va- 

 cuoles in the cytoplasm in which the oil was originally coU' 



