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Show 458 DR. J. s. B O W E R B A N K O N [June 5, they are not so abundantly furnished with tension-spicula, while the retentive ones are the same in form and about the same in number. These organs are not very readily detected in situ while immersed in the sarcode ; and from the delicacy of their structure they require a microscopical power of at least y^-^ linear to render them distinctly to the eye. The gemmules of the sponge are rather numerous on the interstitial membranes, and on the inner surface of the dermal one. They are smooth, spherical or slightly oval, and opaque and black, whether viewed by direct day-light, or, when mounted in Canada balsam, by transmitted light. They vary to some extent in size : the smallest of them measured -jxho m c n m diameter, the largest yrVo" ^nc^J but the average of several measured was y^Vir in(m m diameter. 2. ISODICTYA ASPERA, Sp. 110V. Sponge sessile, multifistulous, fistulae branching irregularly and usually confluent; parietes thick ; surface very rough and irregular. Oscula within the fistulse. Pores inconspicuous. Dermal membrane spiculous, reticulated; rete irregular, uni- or bispiculous ; spicula acuate, same size as those of the skeleton. Skeleton : Rete irregular, diffused; primary fibres multispiculous, secondary fibres irregularly disposed; acuate, stout and rather long. Gemmules membranous, abundant, more or less congregated, spherical, semi-transparent, dark amber-colour. Colour. In the dried state, dark brown. Hab. Abu, Philippine Islands (Dr. A. B. Meyer). Examined in the dried state. Type in the Dresden Museum. This sponge rather exceeds six inches in height, and is of about the same average diameter. The fistulse radiate in all directions from the massive basal attachment, and immediately separate more or less into short stout branches which most frequently become confluent groups. This character of the fistulae is very unusual, and is very characteristic of the species. The surfaces of the fistulae are exceedingly rough and rugged ; and their substance is very brittle in the dried state. Their distal terminations are open to the full extent of their internal diameters ; and their margins are thin. The oscula on the smooth inner surfaces of these organs are distinctly visible by the aid of a lens of about two inches focus. Portions of the dermal membrane, when mounted in Canada balsam ; and viewed with a linear power of about 100, exhibit its reticular structure in a very satisfactory manner ; the rete is rather irregular, but very distinctly exhibited; it is most frequently uni-spiculous ; but occasionally two or, rarely, three spicula are combined in some parts of it. The spicula are nearlv equal in size and of one form only, rather long and stout acuate. In a portion of the dermal membrane thus examined, there were a considerable number of groups of gemmules, each group consisting of numerous closely |