592 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [136] 



EXPLANATION OF PLATE VIII. 



Fig 33 Transverse optical diagrammatic section thronglitlie region of the fin-folds 

 of an embryo cod eigbteeen days after impregnation, sbowing tbe relation 

 of the spinal cbord ms to the cborda dorsalis cAand the intestine i, with 

 the muscle plates pv and segmental ducts sd on either side, x 55. 



Fig. 33 «. Germinal disk of cod's egg divided into four segments, and showing dislo- 

 cation of the second cleavage furrow, x 32. 



Fio 33 1>. Germinal disk of shad's egg of two hours, divided like the preceding, 

 and with the second and third cleavage furrows dislocated, x 18. 



Fig 34 Embrvo cod nineteen days after impregnation. The liver, heart, tail, fin- 

 fo'ld, brain, and intestine have made important progress. The heart now 

 pulsates regularly, but there are as yet no blood corpuscles. The eye is 

 beginning to develop an outer layer of pigment, the lamina fusca. The 

 muscle segments or plates have become more numerous. At the upper 

 right-hand side a bell-animakule, some monads, and an alga are sbowu 

 attached to the vitelline membrane, x 55, 



