MEMORIAL PAMPHLET SHOWING CERTAIN DRAWINGS 



the spaces between them. Numerous short, chitmous spines are developed upon the crust 

 which covers the fibers, and thus we find the polypites arising from a flat, spinous base which 

 adheres to the surface on which the colony is growing. The colony is composed of two kinds 

 of hydranths: sterile feeding-polypites, and reproductive gonostyles. The sterile teeding- 

 polypites are spindle-shaped, being about twice as wide near the oral circlet of tentacles as 

 they are at the base. They have 12 to 1 6 straight, stiff tentacles. The mouth is situated at the 

 apex of a dome-shaped proboscis. They are very contractile and may vary in length from about 

 5 to 15 mm. The reproductive polypites, or gonostyles, are frequently exactly similar in size 

 and shape to the feeding-polypites, and, in fact, are probably merely feeding-polypites which 



have developed medusa-buds 



Differences between European and American medusa of Podocoryne carnta. / ItT^fi > ^1 Tn 



other instances the gonostyles 

 are smaller and more slender, 

 and possess not more than 4 

 to 8 tentacles (see g' , fig. 2). 

 The medusa-buds arise from 

 a zone which is slightly below 

 the circlet of oral tentacles. 

 From 4 to 8 of these buds are 

 usually to be seen upon each 

 gonostyle. According to Mar- 

 tha Bunting, 1894, it appears 

 that the medusa-bud arises as an outpushing of both entoderm and ectoderm of the gonostyle. 

 As the bud progresses in its development, we find the ova in the entoderm of the manu- 

 brium. When a later stage has been reached they migrate from the entoderm into the 

 ectoderm. The spermatozoa, on the other hand, originate in the ectoderm of the inanu- 

 brium, as was shown by Weismann, 1883. When set free the medusa usually has 8 ten- 

 tacles: 4 radial and 4 interradial. The radial tentacles are usually better developed than the 

 interradial and in some individuals there are but 4 tentacles at the time of liberation, the inter- 

 radial ones not yet being developed. 



It is remarkable that while in some stocks of Podocoryne the medusae are set free in an 

 immature state, in others the medusae are mature when liberated, the manubnum being 

 distended with sperm or ova, which are discharged almost immediately after the medusa is 

 set free. It is possible, as Allman, 1871, suggests, that this difference may be due to the influ- 

 ence of local conditions, which may be favorable in the one case and not so in the other to an 

 advanced development of the medusa. Krohn, 1851, and Loven, 1857, have observed stocks of 

 the European form of Podocoryne which were setting free mature medusa?. Indeed, we appear 

 to have a parallel case in Sarsia on the Massachusetts coast, where immature medusae are liber- 

 ated during the early spring months, whereas the medusae become ripe, discharge their genital 

 products, and wither upon the hydroid stock in May. Good figures of Podocoryne stocks which 

 are setting tree immature medusae have been given by Sars, 1846; Hincks, 1868; Allman, 1871; 

 etc. When set free the medusae commonly have 8 tentacles, 4 radial and 4 interradial. The 

 radial tentacles are usually more advanced than the interradial, and in some few individuals 

 there is no trace of interradial tentacles at the time when the medusa is liberated. The manu- 

 brium is short and fusiform and the mouth is surrounded by 4 radially situated, oral tentacles, 

 each of which terminates in a knob-shaped cluster of nematocysts. W'hen set free the medusa 

 is about 0.5 to 0.6 mm. in height. 



In those medusae which are set tree in an immature condition there are at first 8 tentacles, 

 but these increase in number as growth proceeds and finally, when the medusa is about 3.5 mm. 

 in height, there are usually about 32 tentacles, 8 in each quadrant. The manubrium ot the 

 young, immature medusa is slender and fusiform, while in those medusae which are set tree in a 

 mature state it is globular and greatly distended with the genital products. The ectoderm ot 

 the hydroid is slightly bluish and translucent, while the entoderm is creamy-pink or silvery- 

 white in color. 



This species has been found upon the Atlantic coasts of Europe, in the Mediterranean 

 Sea, and from Saldanha Bay, Cape Colony, South Africa. Levinsen, 1893, records it from the 



