86 INVEBTEBRATE MORPHOLOOT. 



aud known as the gonotheca (Fig. 39, go). On account of the 

 presence of these cups the polyps of this order are sometimes 

 termed calyptoblastic. In the typical Campanularian polyjD 

 colonies, such as those of J^ucope or Obelia, no further differ- 

 entiation of the polyps is found, but in the family Plumulari- 

 dse in the neighborhood of each of the small hydrothecse there 

 are one or more slender extensible polyps lacking mouth and 

 tentacles whose endoderm is a solid axial cord, while the 

 ectodermal cells send off long, streaming, pseudopodia-like 

 processes, these polyps apparently playing the part of food- 

 providers for the colony. 



The medussB (Fig. 43) are usually very shallow bells, with 

 numerous hollow tentacles depending from the margin, and 



resemble the Trachymedusse in 

 that the reproductive organs 

 develop on the line of the ra- 

 diating canals. Of these there 

 are in the majority of cases 

 four, though occasionally, as in 

 JEquorea, they may be very 

 numerous. Sense-organs are 

 always present at the margin of 

 the bell and, as in the Trachj^- 

 YiQ. iS.—Ehegmatodes tennis, Ag. medusae and Narcomedusse, are 



always otocysts, the medusae 

 belonging to the vesiculate category. A marked difference 

 obtains between the otocysts of the Leptomedusse and those 

 of the two preceding orders in that the calcareous crystals 

 are in the former developed in ectoderm cells. The otocysts 

 furthermore primitively occur on the inner surface of the 

 velum, where they are lodged in a slight depression, which 

 may, however, deepen so much that the otocysts appear to be 

 imbedded in the substance of the bell. 



In the typical Campanularians free-swimming medusse are 

 developed, and according as the polyps or the medusse attract 

 especial attention the order may be termed that of the Cam- 

 panularise or that of the Leptomedusee. In a few forms, such 

 as Bhegmafodes, up to the present no polyp generation is 

 known to occur, and conversely in certain genera, such as Ser- 



