M. M. METCALF ON THE EYES AND SUBNEUEAL GLAND OF SALPA. 345 



organ, a belief held by many of those who have worked upon the 

 group. To establish this point, if true, one should study the living salpa, 

 making physiological tests. He should also make teased preparations 

 of macerated specimens. I have been unable to secure fresh material, 

 and so could not study the innervation of the funnel in this way. I was 

 able, however, to make out from a study of the preserved specimens 

 some points that indicate a definite nerve supply. 



The funnel and adjacent parts were removed from specimens that 

 had been hardened in Perenji's fluid and preserved in alcohol. The 

 portion removed was mounted in a mixture of glycerine and acetic 

 acid, strongly colored with methyl green. This brought out clearly 

 the nerve fibers, cell outlines and nuclei. In the chain form of Cyclo- 

 salpa pinnata, on the dorsal surface of the walls of the ciliated funnel, 

 there is seen in this way a highly developed plexus of branching nerve 

 cells and fibers (Fig. 9, Plate XLIX). The plexus is closer (smaller 

 meshed) over the posterior portion of the funnel, containing in this 

 region more nerve cells and more fibers than are found further anterior. 

 A pair of strong nerves run forward from the brain over the ciliated 

 funnel and beyond it. These nerves pass directly through the plexus, 

 and were seen in one or two cases apparently to give off very fine 

 branches to the plexus. The actual branching of the nerves was not 

 seen in section, for the nerves themselves are so small as to be traced 

 with difficulty in serial sections, and the exceedingly fine branches would 

 be impossible to find. The most careful focusing with high powers 

 (1735 diameters) indicated that the appearance seen was an actual 

 branching, and not the superposition of the nerve over the fine fiber, 

 or vice versa. 



In the solitary form of Salpa cordiformis-zonaria a similar, though 

 less developed plexus is found over the posterior part of the dorsal 

 tubercle. Two pairs of nerves, the one pair large, the other pair small, 

 run forward from the brain toward the funnel. The outer pair pass 

 over the plexus and beyond the funnel toward the mouth. The inner, 

 smaller pair can be traced to the funnel and about one-third of the way 

 over its dorsal surface, there disappearing. It seems probable that these 

 nerves connect with the nerve plexus dorsal to the funnel, though the 

 opacity of the ciliated funnel in this species rendered the region so 

 difficult to observe that any actual connection was not made out. If 

 there be such a connection the whole structure may be regarded as an 

 apparatus for the innervation of the ciliated funnel. The pair of small 



