OBSERVATIONS ON TPOLYZOA. 217 



larger than the free forms, have no annulus, and in many 

 species the walls of the cells immediately under them be- 

 come so compact and hard, that they cannot be removed 

 from the surface of the wood or stone to which the cell is 

 attached without considerable exertion. 



Certain so called exceptional forms of buds, also, previ- 

 ously noticed by Prof. Allman in Alcyonella fungosa and 

 Lophopus crystallinus, are very abundant in Cristatella, on 

 the interior of the basal membrane* (PI. 13, figs. 2, 3, 8, 9, 

 10, 11, 12, X). They are at first small oval bodies near 

 the border, jutting out from the endocyst of the tubes lead- 

 ing to the second or third line of polypides. Their com- 

 position is similar to'that of the statoblast. They have a 

 thick external membrane and granular contents, but are 

 devoid of a gelatinous envelope, and, also, have a large 

 vacant spot in the interior which is continually varying its 

 shape and position. Simultaneously with them, and con- 

 tinuous with their outer envelope, a long ridge springs up 

 from the endocyst and the outer membrane of the bud, 

 which, becoming membranous, splitting into two portions, 

 and connecting with the upper side of the coenoecium, even- 

 tually incloses them in a tube (PI. 13, figs. 8, 10, 11, Q,). 

 This ridge sometimes passes directly over the centre of the 

 bud, and sometimes to one side, but is almost always 

 present. It occasionally retains the cord like embryonic 

 character, and freeing itself from the endocyst, except at 

 the extremities, forms a pseudo-funiculus, suspending the 

 bud in the coenoecial cavity. The thick external membrane 

 becomes in course of time differentiated from the walls or 

 ridges, and acquires the horny consistency of the casing 

 on the free statoblast, but is never so opaque, or deeply 

 colored. As the outer membrane stiffens no change seems 

 to be made in the granular contents, but the more con- 

 vex face of the envelope sinks, forming an ellipticardepres- 

 sion, and the greater number of the buds become free (PI. 

 13, fig. 12, W). Prof. Allman found them to be hollow, 

 and described this elliptical depression as an aperture. I 

 was, however, unable to substantiate either of these con- 



* ALLMAN. Op. cit. p. 40. 



