of Corynoid Polypes, and its Reproduction. 75 



I have never met with more than seven. The capitate extremi- 

 ties are large and thickly set with thread-cells. 



The polyjies occurred in groups scattered here and there over 

 the bottom and sides of the smaller rock- pools. 



Reproduction. — The Eleutheria of De Quatrefages. 



Reproductive buds are almost always present. They are con- 

 stant in position, forming two clusters at opposite points on the 

 lower portion of the body. Each cluster generally consists of 

 three or four buds in various stages of development, from a 

 simple excrescence on the surface of the body to the fully-formed 

 zooid. 



In its earliest state, the bud appears as a papillary pro- 

 cess both of the external transparent investment and of the 

 opake-white centre, consisting of the endoderm and the somatic 

 cavity (PI. YIII. fig. 4 u). As it increases in size it assumes 

 a clavate form, and becomes attenuated below. As the de- 

 velopment proceeds, the upper portion expands and gains in 

 width, and is gradually moulded into hemispherical propor- 

 tions, while the lower part becomes a slender pedicle or stalk. 

 When this stage is reached, the margin of the distal surface of 

 the zooid begins to exhibit a number of slight crenations, the 

 rudiments of the future tentacles. Soon these crenations are 

 themselves crenated or faintly lobed, and we have an intimation 

 of the bifurcate structure of the arms. There are also very early 

 indications of a difference in character and function between the 

 two branches of the tentacle. One of the lobes into which each 

 of the rudimentary arms has divided becomes somewhat trun- 

 cate, while the other assumes a globular form at the extremity ; 

 and in this part one or two minute thread-cells are soon elabo- 

 rated (PL VIII. fig. d). The latter is ultimately to constitute 

 the true tentacle, while the truncate branch is to take another 

 line of development, and to become an admirable organ of loco- 

 motion. As the growth of the arms advances (but at what pre- 

 cise point I am unable to say), a small pigment-spot makes its 

 appearance at the base of each, on the proximal aspect of the body. 

 To this portion of the structure I shall refer again hereafter. 



The subsequent changes may be summed up as consisting of 

 the gradual enlargement of the hemispherical body, which ulti- 

 mately assumes a yellowish-white colour, the further growth of 

 the arms, and the formation of a round central opening (the 

 mouth) at the distal end of the body and in the midst of the 

 circle of tentacles. 



The forking of the fully developed arm takes place a little 

 above the middle, and the disk-bearing branch is somewhat 

 shorter than that which is surmounted by the globular tip. 



G* 



