86 Mr. E. E. Prince on Oleaginous Spheres in the 



erroneous. Ryder attributes the buoyancy of certain pelagic 

 ova to these structures, and, strangely enough, later observers 

 have put forward the same view, notwithstanding the fact 

 that the most familiar of Teleostean eggs, viz. those of the 

 Salmonoids, possess such spheres in abundance, and yet are 

 wholly destitute of the power of floating. In a list of twenty- 

 two Teleostean ova without large globules, seventeen (or 

 about 75 per cent.) are pelagic. On the other hand, about 

 twenty-four species of Teleosteans are known to possess these 

 globules, and fifteen of these are pelagic, a proportion not far 

 removed from that furnished by the list just named. In other 

 words, the pelagic eggs without large globules are about the 

 same in number as those possessed of globules, so far as 

 researches at present show ; and to explain the buoyancy of 

 floating eggs by the presence of these structures is a manifest 

 fallacy *. Moreover, large globules are present not only in 

 demersal eggs which are littoral, ?'. e. deposited near shore, 

 such as those of various species of Cottus, Lipan's, Gastro- 

 steus, &c., but ova brought up from some depth show their 

 presence also, an example of great interest being the large 

 non-floating egg of AnarrMchas lujjus, which has been reared 

 and studied at St. Andrews for the first time. From an 

 examination of the ovaries of the catfish in February 1884 Prof. 

 Mcintosh concluded that the ova were deposited on the 

 bottom of the sea f, and they have proved to be so ; yet they 

 exhibit a single refringent globule of large size of precisely 

 the same appearance as the globules in the familiar ovum of 

 Cyclojyterus, which is deposited between tide-marks. It is 

 plain that while these globules are of less specific gravity 

 than the remaining contents of the egg^ as is shown by the 

 fact that they always seek the upper side, whereas the ger- 

 minal area descends to the lower side of the ovum, yet they 

 do not produce buoyancy ,• nay, in demersal eggs these 

 vesicles are even more abundant than in pelagic or floating- 

 eggs. Their function is plainly not hydrostatic. A second 

 theory has been put forward by Van Bambeke, viz. that the 

 globules have a nutritive function ; and in speaking of the 

 central globule in the egg of the burbot {Lota vulgaris) he 

 says : — " II n'est pas douteux que la gouttelette refringente 

 centrale remplace ici les dldraents nutritifs qui, chez la tanche, 

 vont s'accumuler sous le germe " |. He adds this important 



* Vide Prof. M'lntosli's observations, * Nature/ vol. xxxi. p. 555 ; Ann. 

 & Mag. Nat. Plist. 1885, vol. xv. p. 435 &c. 



t Ann. & Mag. Nat. Ili.'t^t. Juno 1885, p. 432, and 'Nature,' June 24, 

 1886. 



X Op. cit. p. 6. 



