AND PHYSIOLOGY OP THE SPONGIAD^. 
815 
strongly indicative of the fact that the ovaria, both in an active and an effete state, are 
permanently seated in the sponge, and that the ova only are discharged from it. So in 
like manner the existence of the ovarium in Spongilla reticulata and Brownii, confined 
within a strong spicula case firmly incorporated with the skeleton, is strong presumptive 
evidence of their also being permanent organs, and not of the nature of gemmules 
which separate from the body of the sponge when they arrive at maturity and are ejected 
through the great faecal orifice. 
Many other species of Geodia with which I am acquainted afford these ovaria in 
great abundance, and with some variations in size and form from those in G. IBAndrewii, 
but in no other sponge are they so large and so completely developed. 
Fig. 2, Plate XXXIV. represents an adult ovarium from Geodia IBAndrewii with 
the conical foramen on its summit, and the distal ends of the skeleton spicula flat 
and angular. Fig. 3 represents a small portion of the surface of the same specimen 
as seen with a linear power of 308, exhibiting the flatness and angularity of their distal 
apices. Fig. 4 represents a portion of a young ovarium having the distal ends of the 
skeleton spicula disunited and acutely conical. Fig. 5 represents a portion of a section 
of an ovarium of G. M'^Andreivii, exhibiting the radial arrangement of its component 
spicula. 
In Pachymatisma Johnstonia^ Boweebantk;, a British species common on the rocks in 
the neighbourhood of Torquay, and which I described in a paper read before the Micro- 
scopical Society of London in 1841, these organs assume an oval form ; they are also con- 
siderably depressed. In a young specimen of this species of sponge in my possession, the 
progressive development of the ovaria is very strikingly illustrated. Fig. 7, Plate XXXIV. 
represents an adult ovarium. Fig. 8, one in a semideveloped state, and fig. 9, one of 
the same organs in a very early stage of development. In another species of sponge 
from the South Seas we find a singular variety of this class of ovarium. It is oval in 
form, the length being to the breadth as five to three, but it is so much depressed as to 
appear rather like a dermal spicula plate than an ovarium ; but the radiate arrange- 
ment of its component spicula is perfectly visible with a poAver of 666 linear, and their 
distal terminations as separate and distinct as those of Geodia or Pachymatisma. The 
situation of the foramen is also well defined in many of them. Fig. 10, Plate XXXIV. 
represents a mature ovarium ; fig. 11, a fragment of one to exhibit its degree of thickness ; 
and fig. 12 represents one of the same species of OA^arium in an early stage of develop- 
ment. I have seen four species of sponge which have this description of ovarium ; in one 
it is very considerably longer in its proportions than that represented by fig. 10, Plate 
XXXIV., and in another species it is somewhat shorter. 
Since the preceding portion of the account of the ovaria was written I liaA^e received 
a very remarkable specimen of these organs, which differs materially in its structure 
from any of the forms that I haA’e previously described. The sponge consists of a 
small portion of basal membrane, closely resembling that of a Halichondraceous species. 
It Avas found by my friend Mr. J. Yate Johnston coating rocks and stones at Madeiia. 
