314 



HYDROID^. Part IV. 



wall of the medusa presses more closely upon the contents. In the oldest phase 

 which we have observed, the yolk was divided into innumerable masses {Fig. 8, 

 ae), each of which Avas from one fourth to one sixth the diameter of those of 

 the last stage. The jjlanula, when fully developed, has an oblong form, like that 

 of Clytia (Orthopyxis) poterium. 



The male medusa (PI. XXX. Fig. 17, A B C D, and wood-cut Fig. 50) does not 

 have a peduncle like the female, and yet, in one respect, it attains to a higher 

 degree of development than the other sex, inasmuch as it be- 

 comes possessed of a proboscidal actinostome [Fig. 17, D Iv"), '^' 

 which projects at least through three quarters of the axial 

 diameter. As in the female, the reproductive material of the 

 male occupies the space between the outer and inner wall of 

 the medusa, from the beginning of its development {Fig. 17, 

 A, ae). The medusa develops for a while merely by the gradual 

 separation of the outer wall (/:>) from the inner one (;), while 

 the spermatic mass {ae) keeps the growing interspace constantly 

 filled. Gradually, however, the inner Avail begins to rise above 

 the level of the axis ; but instead of forming a saucer-shaped ^^^^.^^ ^^^^^ ^^ ^^^^^ 

 body, it projects pointedly, at first, like a broad, conical papilla how^hfmal^m;du'?4"i"rf 



,„ .. -i,>Tii , .•, 1 1 T1-1 arranged around the axis of 



(C, k^), and, finally, becomes, at maturity, a broad cyhndncal the hydra. 

 actinostome (D, h^). The spermatic mass always fills the medusa 

 to its extreme border, and, consequently, runs out to quite a sharp edge at its 

 base, where the outer {h^) Avail of the medusa meets that of the axis {y), and, 

 therefore, in a mature state (D), it is more or less broadly and inversely bell-shaped 

 when the medusas are few; Avhen crowded, they assume a more rounded form (Avood- 

 cut. Fig. 50). The spermatic particles (PI. XXXI. A B) have a guitar form {a), 

 with a very slender filament {!>), tAvelve to fourteen times longer than the body, 

 prolonged from the broader end. We have often found the Avhole mass of the 

 axis and its medusas crowded together at the mouth of the calycle (PL XXX. 

 Fig. 18, k), and partly extruded, in a globular mass (A). At first sight, this 

 appearance reminds one of the Avell-developed female medusa3 Avhich Loven saAV 

 groAving at the end of the axis, outside of the calycle of Campanularia (Laomedea) 

 geniculata;^ but, in our animal, it is merely a breaking loose of the reproductive 

 bodies after they have completed the term of their office. 



Proles hgdroidea. — The mode of development of the hydra of this species is 

 essentially identical with that of Obelia. The representations of the tAvo given 



1 Wiegraann's Archiv, 1837, Tab. VI. Figs. 12 Naturelles, 1841. Vol. XV. PI. VIII. Figs. 12 

 and 13; and translated in tlie Annales des Sciences and 13. 



