90 MARGAEET C. COLLCUTT. 



Below the globular region the body again narrows and 

 becomes connected with the basal coenosarc. Miss Bunting 

 (17) has fully described and figured the sporosacs and gene- 

 rative cells of Hydractinia. She mentions that she was unable 

 to trace egg-cells in the ectoderm or mesogloea of the blasto- 

 style. I have^ however, observed small cells situated in the 

 ectoderm of the blastostyle close to the mesoglcea, and indis- 

 tinguishable from undoubted egg-cells in the endoderm of the 

 same region of the blastostyle (PI. 1, fig. 6). 



Also in two cases I have found egg-cells in the mesogloea; 

 the endoderm of the same region already contained several 

 eggs (PI. 1, fig. 7). In one of these cases the blastostyle had not 

 yet formed sporosacs. 



3. The Dactylozooids. — These are cylindrical through- 

 out their length, and are furnished at the distal extremity with 

 a circle of knob-like rudimentary tentacles, from ten to sixteen 

 in number, and crowded with nematocysts. 



They have no hypostome, and are described by Allman (13) 

 and Strethill- Wright (10) as having no mouth. I have, how- 

 ever, found a distinct mouth situated in the centre of the 

 tentacle circle, and leadiug down through a short tubular canal 

 bounded by ectoderm into the endodermal cavity (PI. 1, fig. 8). 

 These polyps are exceedingly muscular, and are capable of 

 coiling and uncoiling themselves. 



In one colony which I examined at Plymouth the dactylo- 

 zooids were frequently branched once or twice, each branch 

 terminating in a typical dactylozooid head. 



4. The Tentacular Polyps. — These polyps are principally 

 situated towards the outskirts of the colony, though they may 

 also occur in the older regions; most frequently I have found 

 them arising from the network of tubes at the growing edge. 

 They are exceedingly slender, though often longer than the 

 other zooids comprising the colony, and are contractile, for 

 their ectoderm is frequently marked by transverse folds. They 

 possess a tubular internal cavity lined by large endoderm cells : 

 I have not succeeded in demonstrating a mouth in these 

 individuals. 



