ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 215 



The neck pedicles of the urns are black. The different colours give 

 the stem a beaded and alternately brown and black appearance. 

 Through the lighter coloured body of the urns a central cord can be 

 seen, extending through the length of the stem. The urn-shaped 

 segments exhibit lateral pairs of cup- like processes, which correspond 

 in position with the branches from the terminal pair of segments of 

 the stem, and apparently indicate branches which have separated 

 from the parent-stem to establish themselves elsewhere as new polyp- 

 stocks. 



A series of specimens of TJrnatella — from such as consist only of 

 a simple cylindrical flexible pedicle, supporting a polyp, to those with 

 long stems, consisting of a dozen segments — indicates the urn-shaped 

 segments to be formed through segmentation of the originally single 

 simple pedicle. The segments, therefoi'e, do not correspond with 

 what were polyps ; but the terminal polyp is permanent, and the 

 segments originate by division from its neck, very much as the seg- 

 ments of the tape-worm arise from its head. After the destruction of 

 the head, the segmented stem remains persistent ; but what becomes 

 of it ultimately has not been determined. Probably the segments 

 may serve the purpose of the statoblasts of other fresh-water Polyzoa. 

 A common mode of propagation of TJrnatella appears to be by budding, 

 the formation of branches with their terminal polyps, and the detach- 

 ment of these branches to establish stocks elsewhere. The different 

 specimens apparently indicate this process, though it was not actually 

 observed. 



Though the stem of TJrnatella is invested with a firm chitinous 

 integument, it still retains its flexibility ; so that when the polyp is 

 disturbed, it not only closes its bell and bends its head, but the 

 entire stem bends, or even becomes revolute. Sometimes the polyps 

 suddenly twist the stems from side to side, as if they had become 

 wearied of remaining longer in the same position. 



Structure and Development of Argiope.* — A. E. Shipley, after 

 an account of the external characters of the two species of this 

 Brachiopod — Argiope neapolitana and A. cuneata — which he has been 

 able to study at Naples, describes the structure of the shell, and 

 discusses the nature of the mantle papillae which make their way into 

 its cavities, the chief function of which appears to be the nutrition of 

 the shell. It is believed that the protrusion of the tentacles is pro- 

 bably effected by the forcing in of a perivisceral fluid, but that their 

 retraction and curling movements are occasioned, in all probability, 

 by the muscular fibres which lie in their interior. There is no anus, 

 and the ileo-parietal band (Huxley) is so feebly developed as to lead 

 to the belief that it cannot afford any support to the intestine ; the 

 liver consists of two branched glands, the secreting surface of whose 

 tubules is increased by the elevation of their inner walls into a 

 number of wedge-shaped ridges. Like other recent observers, the 

 author has been unable to find anything like a circulatory organ, or 

 the system of arteries and " accessory pulsatile organs " which have 



* MT. Zool. Stat. Neapel, iv. (1883) pp. 494-520 (2 pis.). 



