428 DESCRIPTION OF THE PLATES. 



it the Mariana. The ova are seen on each side of the ali- 

 mentary canal ; and in the lower half of the body are the 

 cells containing spermatozoa, which issue from the orifices 

 in the fin near the tail. 

 Fig. 3. Xymjyhon gracile (one oi ihQ Pycnogonidoi) ; natural size. The 

 three circles from which the legs spring convey an inaccu- 

 rate idea of the reality ; they are not cavities, but enlarge- 

 ments of the trunk. 

 ... 4. The same animal in the egg^ just before it is hatched ; greatly 

 magnified. 



PLATE VL 



Fig. L Syngnathus anguineus {Vv^e-^&h), about half the natural size. 

 2. A Comatula rosacea. (Copied from Forbes.) 

 ...3-10. Development of Strongylus auricularis, one of the Entozoa. 

 Fig. 3 shows the primary germ-cell, surrounded by the yolk ; 

 at 4, a division has taken place ; 5, a subdivision ; 6, still 

 further subdivision ; 7, the repeated subdivisions have re- 

 sulted in what is called the '' mulberiy mass," out of which 

 the embryo is gradually envolved as in figs. 8, 9, 10. 

 (Copied from Bagge.) 



PLATE Vn. 



Fig. 1. Terehella nehulosa removed from its tube. The tentacles are 

 both longer and more numerous than here represented ; and 

 the gill-tufts at the side of the head are more apparent. 

 (Copied from Rymer Jones.) 



... 2. An ideal representation of the brain and spinal chord, showing 

 how the nerve- fibres are theoretically supposed to commu- 

 nicate with the nerve-cells of the grey matter of the chord, 

 and thence pass up to the brain, terminating in the cells of 

 the grey matter of the convolutions. (Copied from Leydig.) 



... 3. A Plewohranchus, natural size, seen from above. 



... 4, A stem of the Corkscrew Coralline, natural size. 



PRINTED BY WILLIAM BLACKWOOD \S^ SONS, EDINBURGH. 



