NOTES AND MEMORANDA. 



Observations on the Capitellidae by Dr. Hugo Eisig.— A 

 peculiar organ connected with the alimentary tract of the 

 Capitellidaj has recently been described by Dr. Hu^o Eisi<^, 

 under the title Nebendartn (" Nebendarm d. Capitellidae," 

 * Zoologischer Anzeiger/ No. 7, 1878). This organ, 

 which has been met with in all the main families of the 

 (/apitellidse, consists of a narrow tube on the neural side of 

 the alimentary tract into which it opens in front and pro- 

 bably also behind. The anterior opening is situated close 

 to the posterior boundary of the oesophagus. The position of 

 the posterior opening varies somewhat, and its existence has 

 not been so clearly established as that of the anterior open- 

 ing. The chief interest connected with this organ is the 

 comparison Dr. Eisig has made on the one hand between it 

 and an embryonic organ found in the Ichthyopsida, and named 

 subnotochordal rod, and on the otlier with the siphon of the 

 Echiuoid alimentary tract. The subnotochordal rod is primi- 

 tively a canal split off from the neural side of the alimentary 

 tract for the greater j)art of its length, which soon becomes 

 solid, and occupies a po-^ition (according to Dr. Dohrn's view of 

 the relationship between Annelida and Vertebrata) very simi- 

 lar to that of the Nebendarm of the Capitellidae. The siphon of 

 the Echinoids resembles the Nebendarm in communicating at 

 both extremities with the alimentary tract. Dr. Eisig mentions 

 that Spengel has recently detected iuBonellia an organ similar 

 to the Nebendarm in its connections. The homologies sug- 

 gested by Dr. Eisig for the peculiar organ he has discovered 

 are certainly plausible, but can hardly claim to be satisfac- 

 torily established. 



The segmental organs of the Capitellidae have also been 

 studied by Dr. Eisig ('Mittheiluiigen a. d. Zoologischen Station 

 zu Neapel., Bd. I, Heft I), and the conclusions he has arrived 

 at are of some interest in relation to the possible homology 

 between the vertebrate segmental tubes and the segmental 



