[68 



DESIGN IN NATURE 



PLATE LXVIII 



PLATE LXVIII 



This plate illustrates the arrangements in a calcareous-spiculed sponge, and the position of the monads and 

 spicula, which latter form a rudimentary skeleton. It also shows the remarkable shapes assumed by monads in 

 their amoeboid phases ; likewise cytoblasts of various kinds and at different stages. 



j-je, 1, Calcareous-spiculed .sponge {Grantia compressa, Bowerbank) shows one entire, and portion of a second monad-lined 



chamber x 600. af, Afferent canal for reception of external water ; ef, efferent canal leading to central cloacal chamber ; a, a, 

 collar-bearing monads ; b, swarm gemmule in earlier amoiboid non-segmented phase of development ; c, external defensive spicula ; 

 d, internally projecting tri-radiate spicula. 



Figs. 2, 3, 4, -5, 6, 7, and 8. — Polymorphic forms assumed by collared monads (Grantia compressa, Bowerliank), x 800. It will 

 be observed that the pseudupodic processes on wliich the variety of form depends are in every instance conical-shaped ; the base of 

 the cones being directed tdwards the body of the monad. This is impoitant as showing that these processes are the result of a pushing 

 outwards of the body sarcode by a centrifugal action. The}' are not due to contraction or elasticity of any kind. The same thing 

 happens in all amcebiforin movements. In every case the animal alternately pu.shes or projects its sarcode out of its body by a 

 centrifugal movement, and retracts or withdraws it into its body by a centripetal movement. Amcebiform animals can push out and 

 elongate and retract and shorten portions of their body sarcode at pleasure. Voluntary and involuntary muscles possess similar 

 properties. But for the double power here claimed for living substances and living tissues, movements in plants and animals would 

 be impossible (the Author). 



Figs. 9, 10, 11, 12, 13, and 14. — Isolated amoeboid phases of collared monads of Bread-crumb Sponge (Halichomlria panicea), 

 X 1000. These monads present similar ajipearances to those seen at Figs. 2 to 8 inclusive. The same remarks apply to all (the Author). 



Fkis. 15, 16, 17, 18, 19, 20, and 21. — Metamorphosed collared monads from calcareous-spiculed sponge (Ascetta primonUalis), x 700 

 (Haeckel). Figs. 17, 18, 19, and 20 display characteristic conical-shaped pseudopodic processes in all respects analogous to tho.se already 

 described (the Author). 



Fifis. 22 and i3.— Amoeboid zooids from the cytoblastema ; the former (Fig. 22) showing two nuclei which may either represent 

 the conjugiition of two zooids or a zooid about to divide by fission, x 700 (Haeckel). 



Fid. 24. — Portions of transparent cytoblastema from Leucosolenia coriarca surrounding a poral aperture and containing amcebiforni 

 cytoblasts (a, h) enclosing ingested carmine particles, x 800, 



