110 SIDNEY F. HARMER. 



of sections which it is desired to obtain in given planes. My 

 study of the development of this form has been entirely based 

 on material obtained from this source. 



I have found T. plumosa on the empty carapace of a large 

 crab (Cancer pagurus), but I have not obtained many spe- 

 cimens which I could certainly refer to this species on shells 

 or stones. Its typical habitat may be considered to be the 

 surface of seaweeds from shallow water, but some of the 

 specimens of Tubulipora from shells in deeper water may 

 also belong to the same species. Should it, in fact, prove 

 identical with T. lobulata, Hass., this name would have 

 priority over T. plumosa. 



IV. The Nature of certain Vesicles found in the Tentacles and 

 other Parts, with Remarks on the Structure of the Adult 

 Zooecium and on the Budding. 



The account of the occurrence of these vesicles must be pre- 

 ceded by some statements with regard to the development of 

 the polypide-buds and the structures connected with the orifice 

 of the adult zooecium. 



a. Budding and Structure of Orifice. 

 There are no really detailed accounts of the budding of 

 Cyclostomes, though some information is given by Ostroumoflf 



(32). 



I have not satisfied myself with regard to the manner in 

 which the first rudiment of the bud is derived from the ter- 

 minal membrane. The young bud (fig. 23) is bounded exter- 

 nally by a more or less solid mass of cells of some thickness, 

 which may be regarded as the protoplasmic part of its terminal 

 membrane, and is probably in the main ectodermic. Within 

 this, two or three excretory vesicles appear at a very early 

 stage in all the three species investigated. More internally is 

 a deeply staining two-layered mass of cells, at first forming a 

 hollowed plate, concave externally, but soon taking the form 

 of the well-known vesicular polypide-bud of Ectoprocta. In 

 correlation with the fact that the proximal ends of the zooecia 



