496 MAYNARD M. METCALF, 



in obtaining species from all but two of the families of the whole 

 group, these two families being among the compound Ascidians. 



In the course of the work many points of some interest, not 

 immediately connected with the study of the neural gland, have pre- 

 sented themselves. To some of these reference is made in the later 

 sections of this paper. It has been my endeavor to condense the 

 descriptions as much as possible without sacrificing clearness. Many 

 details have been omitted, yet I fear the descriptive portions of the 

 paper will necessarily prove somewhat tedious. 



It is a pleasure to acknowledge my indebtedness to Professor 

 Whitman, Director of the Marine Biological Laboratory at Wood's 

 Holl, for the facilities there offered me for the prosecution of my 

 work, and to the American Association for the Advancement of Science, 

 whose room at Wood's Holl I occupied for one summer. Professor 

 BuMPUs, Director of the Wood's Holl Laboratory of the United States 

 Fish Commission, gave me a much desired opportunity to collect living 

 Salpas. Dr. H. S. Jennings, Dr. C. P. Sigerfoos and Dr. Reid 

 Hunt have sent me valuable material. To Professor Brooks, under 

 whose direction I began my study of the Tunicates, I am especially 

 indebted for all my specimens of Doliolum, Appendicularia and 

 Octacnemus and most of the Salpa material. Professor Verrill very 

 kindly identified for me several forms from the New England coast. To 

 all of these who have assisted me, I beg to offer my most sincere thanks. 



Advance notices of some of the results here detailed have been 

 published from time to time in the Zoologischer Anzeiger, the Ana- 

 tomischer Anzeiger and the Zoological Bulletin, to which occasional 

 reference will be made in the text. 



Section I. 



The Intersiphonal Organs. 



The term intersiphonal organs is used to refer to the ganglion 

 and neural gland and to the organs connected with them, i. e. the 

 ciliated funnel and the nervous and glandular structures in the dorsal 

 raphe ^). The ganglion is, of course, present in all Tunicates. A 

 neural gland of some sort is also present in every species. One or 



1) The term dorsal raphe is used, as Roule has used it, to mean 

 the median portion of the partition between pharynx and cloaca. 



Roule, 1886. 



