CELL CONSTANCY IN THE GENUS EORHYNCHUS 261 



of the subcuticula, even though the actual discovery of the 

 nucleus by Brown did not come until half a century later. Even 

 as late a worker as Dujardin ('45) observed the swellings on the ex- 

 terior of the body caused by these nuclei, though he did not un- 

 derstand their structure and significance. In regard to these same 

 structures in the body of Eorhynchus agilis (Rud.), Dujardin ('45, 

 p.538) writes: '' .... strie transversalementetpresentantdu 

 cote convexe une serie longitudinale de cinq a six grands pores (?) 

 ou disques orbiculaires,etunseuledu cote concave; . . . . " 

 In speaking of the same species, Saefftigen ('84, p. 9) refers to 

 four or five subcuticular nuclei in the dorsal canal and two in the 

 ventral canal : 



Bei Ech. clavaeceps haben die Subcuticulakerne einen machtigen 



Umfang, ihr grosster Durchmesser iibersteigt oft 0.2 mm 



Sie sind bei dieser Species nur in beschrankter Anzahl, ausschliesslich 

 in den Kanalen, und zwar in den Hauptkanalen, deren ganzes Lumen sie 

 einnehmen, vorhanden. Im Dorsalgefass finden sich ihrer vier bis fiinf, 

 im Ventralgefass zwei, dessgleichen ein bis zwei in jedem Lemniscus. 



Linton ('89, p. 490), in describing what he called Echinorhyn- 

 chus agilis Rud., but was in all probability Eorhynchus cylindra- 

 tus, notes ''large circular spaces in the vascular layer clearly de- 

 fined by a circular thickened ring of connective tissue." Without 

 further delay he accepts the name 'pores' or 'orbicular discs' in- 

 troduced by Dujardin, to whose work reference has already been 

 made. However, Linton's data differ from those of Dujardin, as 

 indicated in the following: "In the specimens which I have ex- 

 amined," says Linton, "there does not appear to be either this 

 regularity or proportion in the arrangement, e.g., one specimen had 

 fom* nuclei on the concave side and two on the convex. In others 

 they could not be made out definitely, but enough could be made 

 out to show they were irregularly placed." However, in justi- 

 fication of modern development of histological methods it would 

 scarcely be proper to leave this statement of Linton's position with- 

 out noting the fact that his studies were upon living material 

 under a compressor. While it is true that a good preparation 

 of a stained toto mount does display the subcuticular nuclei with 

 remarkable distinctness, yet observations of such nature must 



