266 Proceedings of the 



other long and forming a circle round the base of the "buccal 

 papilla. The buccal papilla is striated by crimson longitu- 

 dinal markings, produced by aggregations of the coloured 

 granular matter of the endoderm, and generally continuous 

 with lines passing upwards from the spiral tubes of the poly- 

 pary. In healthy specimens, the buccal papilla is constantly 

 slowly dilating, or contracting, and pumping the fluid con- 

 tained in the polyp backwards and forwards alternately between 

 its own cavity and that which exists below the tentacles, and 

 which, as I have stated, is formed by the anastomosis of the 

 spiral tubes of the polypary. Hence Dalyell has called the 

 polyp the heart of the zoophyte. And one might, though 

 incorrectly, call this the cardiac circulation, and that of the 

 polypary the capillary circulation, of the animal. 



In specimens kept in captivity the flower-like polyp gene- 

 rally drops off, and is renewed every four or five days, and at 

 each renewal a ring, sometimes a circular spathe, is formed by 

 the tip of the old corallum, as the corallum secreted by the 

 growing polyp rises up within it. Hence, the length of the 

 interval between the rings indicates the age which has been 

 attained by each successive polyp. 



I have already stated that three modes of reproduction 

 occur in Hydroid zoophytes. 1st, Oviparous; 2dly, Larvi- 

 parous ; and 3dly, Polypiparous, in which last the young 

 become developed into complete polyps before leaving the 

 ovarian sac, as in the zoophyte we are now considering. 



Thefemale reproductive process in Tubulariahasbeen investi- 

 gated by Baster, Dalyell, and Van Beneden, and their researches 

 have been confirmed by Mummery. The ovarian sacs are 

 attached to stalks which spring from the base of the buccal 

 papilla, above and close to the lower tentacles, and between the 

 crimson striae, and resemble bunches of grapes hanging down 

 on all sides. They are frequently developed in such numbers, 

 and attain so great a size, as to almost hide the polyp in their 

 clusters. The stem of the cluster, and each of the grape-like 

 ovisacs, is formed of the usual three (ectodermic, muscular, and 

 endodermic) layers, and in each ovisac a single ovum, or some- 

 times two ova appear, which become developed into perfect 



