[21] THE EEL QUESTION. 483 



leading us to its final solution. Would that all who possess the necessary 

 means might constantly remember Spallanzani's words, uttered by him a 

 century ago after his many vain attempts to solve the eel problem : " Our 

 still prevailing ignorance regarding the procreation of the eel, instead of 

 deterring us from further investigations, should spur us on to strain 

 every nerve to dispel this dark cloud of ignorance, having ever before us 

 the examples of seekers of truth in other fields of natural science, who 

 by careful and persevering search at last succeeded in removing the 

 seemiugly impenetrable vail from many a mystery of nature." (Opere di 

 Lazzaro Spallanzani, vol. hi, pp. 561, 562, Milan, 1826.) 



appearance of the small lampreys after the spawning season is over. In spite of the 

 most diligent search A. MUller could not find any trace of them except a few dead ones 

 floating about in the water. As moreover the ovaria of these la mpreys never con- 

 tained eggs in different stages of development, as is the case with other fish, hut after 

 the spawning season contained nothing but the empty cells, A. Muller was justified in 

 concluding from this that the organs of generation of these small lampreys are after 

 the spawning-season completely exhausted, and that the fish consequently die. By 

 personal observation I have convinced myself that after the spawning season the ova- 

 ria of the small lampreys are entirely void of eggs, and I must therefore agree with 

 Muller that the supposition seems very natural that the same is the case with Petro- 

 viyzon marinus and Petromyzon fluviatilis. I even go a step farther and ask the question 

 whether, perhaps, such a generative activity, only occurring once during life and fol- 

 lowed by death, is the reason why the eels which have migrated to the sea never 

 return from there." It may not be out of place to poiut to the striking similarity 

 between the generative organs of the lamprey and the eel, to which Rathke has 

 directed attention in his treatise on the organs of generation in fish, not only as regards 

 the female, but, strange to say, also the male eel. 



