802 
DE. J. S. BOWEEBAJS'K ON THE ANATOjVIT 
It is difficult to decide with any degree of certainty what is really the nature of the 
nutriment of the Spongiadse, but in the greater number of species it is probably molecules 
of both animal and vegetable bodies, either living or derived from decomposition. This 
appears to be the case with the greater number of the Halichondroid sponges ; but even 
among them, as well as other genera, there are peculiarities of structure that are strongly 
suggestive of carnivorous habits. Thus, in the first portion of this paper published in 
the ‘Philosophical Transactions’ for 1858, p. 293, I have described among the interior 
defensive spicula a remarkable form, which has been hitherto found in one sponge only, 
the spinulo-recurvo-quaternate spiculum, which “ occurs in great profusion in the cavi- 
ties of the sponge ; clusters of them, consisting frequently of as many as twelve or fifteen, 
radiate from the angles of the reticulations of the skeleton into the interstitial carities of 
the animal.” I have also described, while treating on the internal defensive spicula, the 
recurvo-ternate forms, the heads of which are found projecting their radii, more or less, 
into the interstitial cavities beneath the intermarginal ones in Geodia and Pachymatisma. 
The spinulo-recurvo-quaternate spicula, represented in situ in Plate XXX. fig. 10, and 
the recurvo-ternate ones, figured in situ in Plate XXXII. fig. 2, e, e, e, are both admi- 
rably adapted to destroy the victims entangled among them. 
I have for a long time entertained the idea that these elaborate and varied forms of 
defensive spicula probably subserved other purposes than that of the protection of the 
digestive surface against the incursions of minute annelids and other predaceous 
creatures. They are admirably fitted to retain and make prey of any such intruders. 
No small animal could become entangled in the sinuosities of the interstitial cavities of 
sponges thus armed without extreme injury from the numerous points of these spicula, 
and every contortion arising from its struggles to escape from its painful and 
dangerous entanglement would contribute to its destruction, and it may then, by its 
death and decomposition, eventually become as instrumental to the sustentation of the 
sponge as if actually swallowed by the animal. How far this mode of nutrimentation 
may obtain in the physiology of these creatures it is impossible, in the present imperfect 
state of our knowledge of their habits to say ; but, from the complex, varied, and elaborate 
structure of these organs, and from their evident adaptation to retain such intruders, as 
well as to defend the internal surfaces from injury, it is not improbable that their office 
extends beyond that of the mere defensive function, and that they are, in fact, auxiliary 
organs for securing nutriment for the use of the sponge. If this supposition, that the 
elaborately formed and ingeniously disposed recurvo-quaternate spicula combine the 
office of securing prey with that of defending the interstitial organs of the sponge, be 
correct, it may afibrd a clue to the organic purpose of the recurvo-ternate spicula with the 
exceedingly long and attenuated shafts that so frequently accompany the stout patento- 
temate ones in Geodia Barretti. The apices of these spicula (Plate XXIII. fig. 45, 
Phil. Trans, for 1858) rarely attain the height of the plane of the true connecting spicula, 
and their recurved radii are most frequently projected into the large interstitial spaces 
immediately beneath the plane of the proximal ends of the cells of the intermarginal 
