104 MEDUSA. I, 



therefore, to state their exact number; in well-grown specimens there may be about 200-250 warts. 

 The ectoderm of the warts is somewhat thickened (Plate V, fig. 9). On the abaxial side of some of the 

 warts may be found a small tenon, a rudimentary tentacle. 



The marginal vesicles are very numerous, about half as numerous as the warts; they are 

 situated, with a broad base, in the middle of the adaxial side of the warts, close to the velum (Plate V, 

 fig- 9)- ') Marginal vesicles are never found on warts provided with tentacular rudiment. As all of the 

 material at my disposal has been preserved in formalin and left there for several years, the concretions 

 of the marginal vesicles have been dissolved; according to Allman (1871) the number of concretions 

 in each marginal vesicle varies from 4 to 20 in one and the same specimen. 



The velum is well-developed and as broad as the length of the tentacular bulbs. 



In living specimens the tentacles are said to be light pink. 



Though this medusa is very common in the North Sea and adjacent waters, no descrip- 

 tion has been given since 1848 (Forbes). It was first discovered by G.Johnston (1833) wno made a 

 short description and a somewhat rough figure of the species. A very fine drawing was given by 

 Dal yell (1847 48). The description delivered by Forbes (1848) was rather incomplete. A few mor- 

 phological remarks are found in the works of Allman (1871) and Bohm (1878). The description in 

 Haeckel's monograph (1879) is based on the descriptions and drawings of Dalyell and Forbes. - 

 The records on the occurrence of the species are likewise rather few. It is no wonder, therefore, that 

 Mayer (1910, p. 319) has an entirely incorrect interpretation of the relationship and distribution of the 

 species. Mayer suggests that Tima bairdii may prove to be the young of Tima formosa which is 

 found off the Atlantic coasts of New England, and that it is an arctic form occasionally appearing at 

 the coasts of Scotland. 



Tima formosa L. Agassiz reaches twice the size of Tima bairdii and has about 32 tentacles 

 of three different sizes; according to Bigelow (1913, p. 36) the number of tentacles may amount to 

 39; it has about 100 marginal warts, whereas Tima bairdii, though it is a smaller species, may have 

 more than 200. Mayer (1910, p. 317) and Bigelow (1913, p. 36) confirm the statement of A. Agassiz, 

 that the marginal vesicles in Tima formosa alternate with the warts, being placed in the spaces be- 

 tween the latter; in Tima bairdii they are placed on the warts themselves (see abovej. The two species 

 may be nearly related to one another, but they are clearly distinct species. 



More peculiar is the suggestion of Mayer (1910, p. 319), that Tima flain'labris Eschscholtz 

 might be the young of Tima formosa. It is not very likely that a large species with about 80 short 

 tentacles might be a young stage of a smaller medusa with only 32 tentacles. Tima flavilabris Esch- 

 scholtz from the Azores is, without any doubt, identical with Tima lucnllana Delle Chiaje from the 

 Mediterranean, flavilabris being the correct name of the species 2 . 



Besides the species already mentioned, we know another Atlantic species of Tima, viz. Tima 

 teuscheri Haeckel from the coast of Brazil, possessing 8 long and 40 short tentacles. 



'( A. Agassiz in his description of Tima formosa states that the marginal vesicles are situated in the spaces between 

 the warts. 



2 ) The question of the correct name of this species will be discussed in a later work. 



