IN SPONGILLA FLUVIATILIS. 59 



of the same general type. So here is another variation which has 

 not yet appeared, for, though allying itself with that of Henley, it 

 has still its distinction from it. The membranes are more developed 

 and require the sustaining spicula thus provided ; but it would not 

 be difficult to show, in other examples, a step in this direction. But 

 the most interesting fact in connection with it is the occurrence not 

 only of the ovaria, so well known, which are to be seen here in every 

 stage of progress, but also of that form, which occurs so often in the 

 silicious sponges as the reproductive organ, generally termed the 

 gemmule.* This is the first time that I ever saw or heard of this 

 as occurring in the freshwater sponge, and it is often found in close 

 proximity to the ovaria. The fact, however, is suggestive of the 

 necessity of further research into the real part these organs play in 

 the life economy. The birotulate spicule is very long in the shaft, 

 thus bearing analogy with that at Henley (fig. 4) . 



A sponge found at Hertford, of which mere fragments came to 

 my hand through our friend, Mr. Priest, to whom I have been much 

 indebted for specimens, appears to be of the same character as that 

 from Ditchleys, especially as regards the occurrence of the gemmule, 

 but it appears to want the delicate spicules of the membranes ; my 

 specimens, however, are not sufficiently good for me to determine 

 this with precision. 



I have now, then, gone through the varieties, but in my search for 

 the typical Spongilla I applied to Mr. Fullagar, of Canterbury, a 

 gentleman well known to us, as a correspondent, and to whose 

 courtesy I am indebted for a specimen which he procured at Bolton 

 Mills Pool, near that city. Being always particular as to the 

 locality and to the conditions under which an object of natural 

 history is found, Mr. Fullagar communicated to me, in answer to 

 enquiry, that it grew " on the bars of the grating, which is placed in 

 front, to prevent the weeds, &c, from going to the water-wheel. 



* When naturalists have not yet determined the exact offices of the 

 several organisms, it is difficnlt to distinguish them by a name. Gemmule, 

 seed-like vessel, spore-case, ovarium, have all been given to the 

 well-known forms connected with reproduction in the Spongillae. 

 I have used Dr. Bowerbank's term, which he adopted, as against 

 the gemmule ordinarily found. To this latter Mr. Carter would apply the 

 term ovisac ; more accurate, probably, for it is certainly no gemmule in the 

 true sense of the term. But "ovisac" and "ovarium" are synonymous, 

 and we cannot use both. In using here the term " gemmule " it will only 

 be for the distinction of one object from another, not as assenting to the 

 propriety of this term, any more than some naturalists do to that of 

 " ovarium'* given to the seed-like vessel. 



