330 HYDROID^. Part IV. 



Between this and the inner wall of the disk, the reproductive material, the sper- 

 matic (sj)) or the ovarian mass {ov), is dejsosited. 



Emhrijolocjij. — Although the breeding season commences in May, it is not until 

 June that any of the ovarian or spermatic bodies have attained maturity ; at the 

 latter date, Ave have secured and figured {Figs. 11, a h c, and IG, A B C) the 

 ripe spermatic particles, and the egg. The egg consists of a very thin, vitelline 

 sac {Fig. IG, B ?•) ; a perfectly homogeneous, or uniformly and minutely granular, 

 dark yolk [g], the granules appearing as mere dots (A), rnider a magnifying power 

 of five hundred diametei-s ; a clear, Purkinjean vesicle (B p, C 2^)7 ^^^^ ^ thick- 

 walled, homogeneous, Wagnerian vesicle («'). In a fully-developed medusoid, the 

 eggs are so crowded upon each other, as to be irregularly polyhedral, but upon 

 being set free, they assume perfectly curved outlines, almost, or quite spherical. 

 The spermatic particles fill the male medusoid {Fig. 8) in one uniform mass {sp) ; 

 they are comparatively very minute, so that, as seen with a power of five hundred 

 diameters {Fig. 11, a), it is impossible to represent their proper form, and, therefore 

 we have drawn them on a diagrammic scale {Fig. 11, h c), and in two positions, 

 showing that from one side they are pear-shaped {h), and from the side at right 

 angles to the latter they are oval, and have a slender filament, about four times 

 as long as the body, appended to the narrower end. 



Budding. — The main stem increases in length by terminal growth {Fig. 12,^); 

 the extreme apex {h) is constantly developing new cells, and a chitinous sheath, 

 which gradually become lateral by the onward progress of the newer portions. 

 At certain points, corresponding to the bases of the hydra-calycles, the stem 

 broadens as it grows, the walls become extremely thick, especially the outer one 

 {Fig. 14", a), and the inner walls become three-lobed {c <? e"). At the lower 

 part of the bud, the cellular structure of the outer wall («) is barely intimated 

 by fine transverse strife ; but above, the cellular structure is quite evident, seeming 

 to be a congeries of coarsely granulated, oval cells, arranged end to end in rows 

 which traverse the thickness of the wall. Those cells which lie in the youngest 

 part, or terminal portion of the bud, have a transparent, thin wall {Fig. 13, a b c), 

 which is thickly lined by a layer of globular particles {d) ; others, from this 

 neighborhood, but a little older {Fig. 13, c f g h i), appear to have thick Avails 

 (/), and homogeneous, highly refractive contents, and are rather elliptical than oval 

 in outline. The inner Avail (e) shoAvs more of its cellular nature, in the older por- 

 tions, than the outer wall. The chitinous sheath (c) is very thick beloAV, and very 

 clearly shoAvs the sujjerposed lamellae, of Avhich it is composed ; but it thins out 

 quite rapidly, and is a mere film across the end of the bud. In the next stage 

 Avhich Ave have to present, the slight triple lobulation of the last, has become 

 fully three-parted {Fig. 17, / f^ f^), reminding one very much of a three-toed. 



