ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 97 



hermaphrodite, the rest having female cells only. As some large forms 

 were found without brood pouches, and a number of very small ones with 

 the pouch well developed, the period of reproduction must either vary with 

 individuals, or must be periodic. 



Gastroblasta Raffaelei.* — Dr. A. Lang describes a remarkable cras- 

 pedote medusa which he observed at Naples ; almost all the individuals 

 examined had more than one stomach and a varying number of apparently 

 irregularly-arranged tentacles and radial canals ; one large individual had 

 nine gastric tubes ; so that it appeared to him that he had before him a 

 colony of medusae formed by a kind of incomplete division. 



The example just mentioned had its greatest disc-diameter 4, and its 

 smallest 2 7 mm. ; all the other examples were much smaller. The form 

 taken for description had the disc slightly curved, the gelatinous substance 

 poorly developed, the velum pretty broad and powerful. The outer circum- 

 ference of the disc is not circular, but somewhat ellipsoidal ; at the margin 

 tentacles and tentacle-buds were found at various stages of development. 

 Between them were ten auditory vesicles formed on the leptomedusan type. 

 Of the four gastric tubes not one is central ; each gave off a radial canal, 

 which opened into the well-developed circular canal. 



A study of the tentacles showed that the margin of the umbrella was 

 divided by the four that were oldest into four quadrants of unequal size ; 

 Jihe relative positions of the various tentacles is exactly stated. The 

 ten auditory vesicles were found to be of various ages, and seem to appear 

 much later than the tentacles; similarly the four radial canals were of 

 different ages. The tentacles are hollow, and much thickened at their 

 base ; the urticating capsules are arranged in more or less distinct rings ; 

 in structure the tentacles resemble those of Eucope and JPhialidium. The 

 gastric tubes are unstalked, tubular, and capable of considerable enlarge- 

 ment ; each is produced into a large quadrangular oval disc, which is very 

 contractile ; the wall of the stomach is very thick, and of the disc very thin. 

 The constancy in the number of four gastric processes is the sole anatomical 

 characteristic which points to the primitive quadriradiate structure of the 

 Medusae. New gastric tubes arise as outgrowths of the radial canals which 

 project into the cavity of the subumbrella ; and, on superficial examination, 

 they may be mistaken for gonads. 



Division is one of the means by which this remarkable form reproduces 

 itself, and the plane of division is at right angles to the connecting vessel 

 between the oldest and next oldest stomach, and is also at right angles to 

 the longest diameter of the disc ; the organs in each half correspond exactly 

 in number, arrangement, and age-series, allowing, of course, for the fact 

 that each half cannot have exactly the same parts ; that is, if the right half 

 be called A, and the left B, the oldest tentacle (t) of the mother becomes 

 the oldest tentacle of A, the second oldest the oldest of B, the third oldest 

 of the mother the second oldest of A, and so on. It is, in fact, possible to 

 say of either to which half of the mother it corresponds. 



The author next describes the metamorphosis of the daughter animal 

 which arose by division ; if the starting stage be that of the left half of the 

 dividing medusa, the second stage is marked by the development of fresh 

 tentacles and a new radial canal ; in the third there is, inter alia, a new 

 stomach developed, and in the fourth a fresh mouth. The result of all this 

 is that the daughter is now exactly like the mother. There may be now a 

 fresh fissure, in which the same phenomena as before are seen, or there 

 may be further budding ; in the latter case there may come to be 26 well- 



* Jenaiseh. Zeitschr. f. Naturwiss., xix. (1S86) pp. 735-63 (2 pis.). 

 1887. H 



