Observations on British Zoophytes and Protozoa. 159 



contains numerous granules, and this ectoderm is continued 

 over the cells, they, like the thread-cells of other animals, 

 being buried within it. A still more remarkable error is 

 committed by the learned author in describing the cells as 

 being able to protrude their lassoes or threads through an 

 opening in the summit of the cell and again retracting 

 them, and further, in imagining that the threads are in- 

 struments of prehension. A very careful examination has 

 assured me that what he has mistaken for protruded threads 

 are indeed prolongations of the sarcode of the ectoderm 

 analogous to the processes of the Ehizopods, and to similar 

 processes which are found over the thread-cells of other 

 animals. In Cydippe, however, they more readily retracted 

 and extended than in the other cases. 



3. On the Stem-Canals o/Tubularia indivisa. 



In the fourth volume of Agassiz's " Contributions to the 

 Natural History of the United States," the author has noticed 

 a paper of mine on the stem-canals of this zoophyte, which 

 I have represented of equal size, and running along the 

 stem within the ectoderm. Having described the canals 

 in the stem of Tubularia Gouthouyi, and found one of these 

 canals larger than the others, he remarks, " We find the 

 large and the small channels also in a very closely allied 

 species, the Tubularia indivisa of Europe, sent to us by 

 Sars from the coast of Norway ; and if the observations of 

 Dr Wright were made upon the same species, then his dis- 

 covery, although very interesting, is a partial one." I have 

 again repeatedly examined the stem of Tubularia, and find 

 that although one or several enlarged tubes occasionally 

 exist, it is by no means of constant or frequent occurrence. 

 In this zoophyte there is no ground for stating that it exists 

 and constitutes, according to the theory of Agassi z, the 

 broad chyliferous cavity of the stem. 



