On tlie conuective tissues and body cavities of the Neinerteans. 5 



intercellular substance, 2) mesenchyni, 3) pareuch y m, 

 4) the intracapsular tissue of the nervous system, 5) the 

 interstitial connective tissue of the body epithelium, 

 6) the pigmented, branched connective tissue cells of 

 the body wall (this latter only in Linens). I have also attempted 

 to express the probable ontogenetic development (histogenesis), of the 

 tissues in question. The terms "gelatinous tissue" (Hubrecht) and 

 "body parenchym" (Bürger), which have led to much confusion, and 

 in fact greatly retarded our knowledge of the connective tissues, will 

 not be employed. 



I wish to express my thanks to Dr. Alexander Agassiz, for 

 the opportunity to work in his private laboratory at Newport, and 

 to the U. S. Fish Commission, for the use of its Station at Wood's 

 Holl, during last summer. My obligations are further due to the 

 Directors of the Wistar Institute of Anatomy and Biology, for the well- 

 equipped laboratory placed at my disposal. 



Material and Technique. 



In regard to the synonomy of the species herein enumerated, the 

 reader is referred to the appendix on classification. 



Teirasfemma vermiculum I found abundantly between tides, oij 

 fucoid sea- weeds at Newport, E,. I. ; at Wood's Holl, Mass., this 

 species is represented by T. catenulatum, which occurs in similar 

 localities. I collected both the red and green color-varieties of Linens 

 gesserensis on the shore at Newport, usually near high-water mark; 

 while I found only the green variety at Wood's Holl, where it is 

 abundant in the so-called "Eel Pond" — a little inlet of the sea — 

 among the roots of water plants. L. lactens 1 found in large num- 

 bers in a salt-water aquîtdum of the Berlin Zoological Laboratory; 

 and I collected SticJiostemma eilhardi from two freshwater aquaria 

 of the same laboratory. Several specimens of Carinella annulata 

 were kindly collected for me at Bergen, Norway, by my friend 

 Dr. F. ScHAUDiNN, of the University of Berlin. One immature spe- 

 cimen of Cereh-atulus lactens I found at Wood's Holl, in the sand 

 at low water mark. Amphiporus virescens is abundant at Wood's 

 Holl, on sea-weeds between tides, and among roots in the Eel Pond; 

 A. glutinosus is also found in this Pond, though in smaller numbers 

 than the preceding species. 



The results of my experiments with fixatives and stains shall be 



