GEMMATION. 37 



The development of the bud in the species with crescentic lophophore is essentially the 

 same as that just described. The first appearance of the bud in Lophopus is seen near the 

 orifice of the cell, as a minute spherical tubercle (PI. XI, fig. 10), projecting from the inner 

 surface of the endocyst into the perigastric space. It is evidently composed of a mass of 

 minute cells with a more condensed peripheral layer. It now increases in size, and a clear, 

 oval space becomes apparent towards one side of it (fig. 1 1). This space soon acquires a 

 triangular figure (fig. 12), and it is now evident that the lophophore has begun to develop 

 itself from its walls, and that the triangular space corresponds to the interval between the 

 two arms of the rudimental lophophore. By this time the young polypide has become removed 

 from the surface of the endocyst of the parent cell, to which it is now only connected by a 

 membranous sac which suspends it in the perigastric space of the adult, and which ultimately 

 becomes the tentacular sheath. At the same time, the alimentary canal begins to appear as a 

 minute cavity in the part of the bud farthest removed from the walls of the cell. This cavity 

 increases in size (figs. 13, 14), and becomes the stomach, while the intestine also shows 

 itself as a tubular process on one side of the bud (fig. 13). The lophophore, which from its 

 earliest appearance is distinctly bilateral, now presents the form of a semicircle, with a 

 bilobed base, and thickened margin ; as yet, there is no trace of tentacula. The retractor 

 muscles show themselves as two fasciculi passing off from the base of the lophophore, and 

 the funiculus may also be seen attached to the posterior extremity of the body. The tentacula 

 now make their appearance as minute tubercles upon the thickened margin of the lophophore 

 (fig. 15). The tentacula and arms of the lophophore are then simultaneously elongated 

 (fig. 16), while the three regions of the alimentary canal, oesophagus, stomach, and intestine, 

 are easily distinguishable, and little more is now wanting than an opening through the walls 

 of the parent- cell into the tentacular sheath of the young polypide, to complete the develop- 

 ment of the gemma. 



Statoblasts. 



In all the fresh- water phylactoltematous Polyzoa, bodies of a very peculiar nature 

 occur at certain seasons, lying loose in the perigastric space. To these bodies, for reasons 

 to be presently mentioned, I propose to give the name of Statoblasts. From the earliest 

 period that the fresh-water Polyzoa became an object of stud}', the statoblasts attracted the 

 attention of observers. Their form is not exactly the same in the different species, but they 

 may be generally described as lenticular bodies, varying, according to the species, from an 

 orbicular to an elongated oval figure, and enclosed in a horny shell, which consists of two 

 concavo-convex discs united by their margins, where they are further strengthened by a ring 

 which runs round the entire margin, and is of a difierent structure from the disc (PI. I, 

 figs. 3 — 8 ; PI. IV, figs. 4, 5 ; &c.) In Fredericella alone is the marginal ring so little 

 developed as to be scarcely apparent. In all, one side would seem to be slightly more convex 

 than the other. 



In all cases, except Cristatella and Pectitiatella, the statoblast is destitute of any further 

 appendage ; in these two genera, however, it is furnished, when mature, with hooked spines, 

 which, at least in Crisiatella, spring alternately from the two sides just within the annulus 



