Mr. H. J. Carter on Fossil Bponge-spicules. 209 



accords with the evolution of the animal kingdom in its diffe- 

 rent stages, that there must be a period in both instances 

 where the phenomena of life are independent of any brain or 

 nervous system such as we understand it. 



Again, there is a variety or individuality in this " blind 

 instinct " which must exist before the chemical and physical 

 influences are brought to bear upon the original " particle of 

 protoplasm," whose particular development is by this parti- 

 cular instinct insured; for no two individuals are exactly 

 alike, to say nothing of specific differences ; while the subse- 

 quent existence of this "particular instinct," after the deve- 

 lopment has fulfilled all that is required of it, may be in- 

 ferred, just as the leaves in autumn, after having fallen 

 from a deciduous tree, to return to the dust from which they 

 originally came, are succeeded by a similar development 

 the following year under a similar instinct — or as the butterfly, 

 perishing after the act for which all its elaborate metamor- 

 phoses have been passed through has been completed, appears 

 again another year under similar circumstances. 



EXPLANATION OF PLATE XIV. A. 



Fig. 1. Spirogyra endeavouring- to conjugate with Claclophoru. ««, two 

 cells of Spirogyra connected ; b b, remains of spiral bands or 

 gonimic contents ; c, septum ; d d, two bunches of root-like 

 processes, respectively applied to e, filament of Cladophora. 



Fig. 2. The same, a, single cell of Spirogyra ; b b, remains of spiral 

 bands or gonimic contents; c, bunch of root-like processes 

 applied to d, filament of Cladophora. 



Fig. 3. The same, a a, two cells of Spirogyra disconnected ; bbb, re- 

 mains of spiral bands or gonimic contents ; c c, bunches of root- 

 like processes applied to d d, two connected cells of Cladophora ; 

 e e, gonimic contents ; /, septum. 



XXVII. — On Fossil Sponge-spicules from the Carboniferous 

 Strata of Ben Bulben, near Sligo. By H. J. CARTER, 

 F.E.S. &c. 



[Plate XIV. B. figs. 1-17.] 



In the last contribution that Mr. James Thomson made to 

 our knowledge of fossil sponges which existed during the 

 Carboniferous epoch in the neighbourhood of Glasgow (' An- 

 nals,' 1879, vol. iii. p. 141, pi. xxi.), I described and illus- 

 trated Holasterella conferta, a genus of sponges, as the name 

 indicates, exclusively composed of stelliform spicules, whose 

 typical figure, from the same locality, had been found and 

 illustrated a year previously. At the same time I added 



