Mr. H. J. Carter on the Reproduction of Sponges. 421 



the Spongiadee, whichever appellation may be thought most 

 appropriate, it is, in its passive form, a minute globular cell, 

 apparently filled with granuliferous plasma, bearing a nucleus 

 and two contracting vesicles, provided with a rostrum or pro- 

 jecting cylindrical portion supporting a delicate fimbriated 

 collar, in the midst of which is a single cilium, and, in its 

 active state, will take into its body crude material (that is, 

 particles of indigo) if they be presented to it. The collar and 

 rostrum possess the power of polymorphism ; and, when neces- 

 sary, the whole body can be thus transformed. The latter is 

 about l-3000th of an inch in diameter in the calcareous sponges, 

 and only half that size in those of the siliceous ones that I 

 have examined ; and they are arranged in countless groups 

 on the lining sarcode of the areolar cavities of the sponge. 



Of all other animalcules or Infusoria with which I am ac- 

 quainted, the sponge-animal seems to me to come nearest to 

 Diffiugiaj or to that kind of Amoeba which throws out its 

 pseudopodia from one part of its globular form in particular 

 (see an illustration of this in 'Annals,' 1856, vol. xviii. pi. 5. 

 fig. 17). Hence it may be inferred that, if among the sponge- 

 animals we find instances of two in apparent union similar to 

 that which is termed " zygosis" among the Diffiugice^ we have 

 strong reason for believing that in both instances this kind of 

 union is for the same purpose. 



In zygosis of the Diffiugice the mouths of the two tests are 

 brought together by an apparent union of the two contained 

 animals ; and if this be watched, the two animals thus united 

 will be observed to flow backwards and forwards into each 

 other's tests, as if their incorporation was as complete as the 

 union of two drops of water ; after which they separate, and 

 each betakes itself to its own test. 



Of this process Mr. W. Archer, of Dublin, who is probably 

 the highest authority living, from his extensive and actual 

 observation of the nature and habits of these animals, states 

 respecting zygosis : — " Whatever may be the significance of 

 the phenomenon, it is at least one which I have noticed my- 

 self in nearly every form of all the genera [of the freshwater 

 Rhizopoda], each individual species always conjugating only 

 with its own fellow " (Quart. Journ. Microscop. Sc. April 1871, 

 No. xlii. p. 111). I can confirm Avhat Mr, Archer has stated; 

 and in one instance I found five Difflugke of the same form 

 and species, which is one of the largest, viz. D. urceolata^ Cart. 

 (Annals, 1864, vol. xiii. pi. 1. fig. 7), all united together by 

 their mouths, after the manner of zygosis. But, whether they 

 be found united in pairs, which is the usual way, or in greater 

 number, they are always, as Mr. Archer has stated, of the 



