ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 357 



heart-urchin requires 18 to 20 days as compared with 6 to 8 weeks in 

 the regular sea-urchin. The young Echinus, with its horizonal radial 

 canals ending in unpaired tentacles, is really an Asterid, whereas the 

 youug Echinocardium, with its meridional radial canals terminating in 

 sensory knobs and its central anus, is really a regular sea-urchin. It 

 illustrates tachygenesis. It follows that the whole history of the 

 changes converting the regular type into the Spatangid type is contained 

 in the post-larval development of Echinocardium, but this is very 

 difficult to follow. 



The author's principal results are as follows : — 1. Only one pore- 

 canal is developed ; it is formed as a vertical outgrowth from the left 

 anterior coelom which meets a shallow indentation of the dorsal ecto- 

 derm. 2. Although there are no teeth, five dental sacs are formed in 

 the larva ; they give rise to spines with a ball-and-socket joint. 3. The 

 left anterior coelom becomes modified into an axial sinus, but this — in 

 contrast to what occurs in regular urchins — remains small and becomes 

 vestigial in the adult. 4. A large madreporic vesicle is formed, arising 

 as a dorsal outgrowth of the right anterior ca3lom. 5. The hydrococle 

 sends out five lobes which become the radial canals of the water-vascular 

 system ; the tips of these canals terminate in sensory knobs, but they 

 never project freely as unpaired tube-feet as they do in the larva3 of the 

 regular sea-urchin. 6. From the basal portions of the radial canals 

 there arise a series of five freely projecting tube-feet, one from each 

 canal. These tube-feet are the only ones which the young sea-urchin 

 has when it assumes the adult form. They become the buccal tube- 

 feet. 7. The young sea-urchin when it assumes the adult form has an 

 anus in the centre of the dorsal surface, and the intestine is curved in a 

 reversed coil like that of a regular sea-urchin. 8. All the spines of this 

 stage are similar to those of a regular sea-urchin, except those of the 

 sub-anal fasciole which are precociously developed. 9. After meta- 

 morphosis the epithelium of the larval gut undergoes ecdysis, just as in 

 one. of the higher insects. The epithelium of the adult gut is regenerated 

 from pockets of cells which remain in the embryonic condition. At the 

 same time the gut shrinks greatly in diameter, and the volume of the 

 ccelomic cavity increases. It seems that an important factor in meta- 

 morphosis is alteration in the permeability of the gut-wall. J. A. T. 



Coelentera. 



Palasozoic Victorian Hydroids. — Fredekick Chapjian {Proc. Boy. 

 Soc. Victoria, 1919, 31, 388-93, 2 pis.). Descriptions are given of 

 Archseolafoea longicornis g. et sp. n. like Lafoea, Mastigograptus montgettae 

 g. et sp. n., Archseocryptolaria g. n., with two species, near Cryptolaria. 



Australian Hydroids. — W. M. Bale {Proc. Roy. Soc. Victoria, 1919, 

 31, 327-61, 2 pis.). It is pointed out that in its most important peculiarity 

 — the form of the oral portion of the hydranth — Broch's BonnevieUa 

 agrees absolutely with SiUcularia undidata and Orthopyxis caliculata. 

 A description is given of SaccuUna arenosa g. et. sp. n., a curious zoophyte, 

 perhaps the same as Lamarck's Tihiana ramosa. It has string-hke 

 monosiphonic stems, singularly irregular in form, with numerous 



