CELL CONSTANCY IN THE GENUS EORHYNCHUS 267 



in no case has more than a smgle one. Figures 22 and 43 indicate 

 clearly this relation of the nuclei in the lemnisci. 



An obvious explanation of the cause of so many investigators 

 going astray on the question of the number of nuclei in the lemnisci 

 is found in the generally accepted conclusion that these are 

 paired lateral organs. Therefore as soon as two nuclei were 

 demonstrated in one of them it was the natural thing to expect 

 a duplication of this condition in the organ of the other side 

 of the body. Failure to recognize both nuclei in each of the 

 two lemnisci could be accounted for by the interference of 

 overlying parts. Or even in case serial sections were examined 

 in this connection the lemnisci are usually so much twisted and 

 coiled about one another that, unless reconstruction drawings 

 are made, one is not sure of the interpretation of the numbers 

 and relationships of the nuclei. 



.Eorhynchus gracihsentis. The small size of the lemnisci in 

 this species, and the fact that their usual condition is a mass of 

 twists and turns in the anterior end of the body, together serve 

 to render an accurate analysis of the exact structure very perplex- 

 ing. The careful study of serial sections of numerous individ- 

 uals fully demonstrated the inequality of the two organs. Invar- 

 iably one lemniscus was found to be supplied with two large 

 nuclei lying in the axis of the canal, while the other contained but 

 a single nucleus in its canal. These nuclei so closely resemble 

 those of the subcuticula that no special description seems neces- 

 sary for them. In shape they are more elongated and display 

 more of a tendency toward a pointed condition at either end. 



Eorhynchus longirostris. In this species the lemnisci demon- 

 strate the point in question most admirably (fig. 22). Here re- 

 constructions from serial sections were needless, since the nature 

 of the lemnisci was such that each stood out as a distinct, practi- 

 cally straight tube extending backward into the body cavity. An 

 examination of toto mounts was sufficient to demonstrate that one 

 of these organs possessed two nuclei of the subcuticular type 

 while the other had but a single nucleus. 



Eorhynchus emydis. It was from the study of the whole 

 mounts of immature forms of this species that the writer first 



