440 THE ANIMAL KINGDOM. 



there are a few oval red haematids. A tubular ciliated saccule, extending 

 on the left side from the margin of the mouth to close behind the velum, 

 where it opens into the pharynx, is supposed by Hatschek to represent a 

 kidney, and to be homologous with the infra-neural gland of Urochorda. It 

 is said to be mesodermic in origin. Ray Lankester has pointed out the 

 existence of two tubes, one on each side, opening into the posterior region 

 of the peribranchial cavity at one end, and at the other into the coelome (?). 

 They are possibly renal. The coelome in the region of the body behind 

 the peribranchial cavity is capacious, and contains a coagulable lymph. Its 

 extensions forward above the pharynx and into the epipleures are 

 small. 



The ovaries and testes are segmentally arranged, and lie about the 

 level of the union between the lateral trunk and ventral transverse muscles. 

 They consist at first of masses of cells lying beneath the inner wall of the 

 epipleures, from which they are probably derived. A central cavity appears 

 in each mass, and the cells, which are now placed peripherally, develope 

 into ova and spermatozoa respectively. The ripe products appear to be 

 set free by rupture of the inner epipleural wall into the peribranchial 

 cavity, whence they may escape by the abdominal pore ; sometimes, how- 

 ever, through the branchial slits into the pharynx, and thence by the 

 mouth. The ovum undergoes total, and at first fairly regular segmentation. 

 There is an invaginate gastrula, and the coelome is an entero-coele, which 

 is divided from before backwards into a series of paired sacs, the primitive 

 somites ; see p. 334. It may be added to what is stated there that the two 

 anterior paired sacs grow forward into the head on either side of the 

 notochord, and that an anterior sac, at first single, then dividing into a 

 right and left half, originates from the fore-end of the archenteron. The 

 left sac remains small, acquires an opening to the exterior, and becomes 

 the organ of taste or smell mentioned above p. 438. The right sac 

 increases in size, and takes up a position anterior to the mouth and below 

 the notochord. Hatschek does not state its ultimate fate, but it gives 

 origin presumably to mesoblastic structures. A somewhat similar anterior 

 entero-coelic pouch is seen in the larva of Balanoglossus : see Enteropneusta 

 among Vermes. 



Ray Lankester, Q. J. M. xv. 1875 ; Langerhans, A. M. A. xii, 1876; Rolph, 

 M. J. ii. 1876; Schneider, Beitrage zur Vergleich. Anat. Berlin, 1879; Balfour, 

 Q. J. M. xx. 1880; Rice, American Naturalist, xiv. 1880; Rohon, Dk. Akad. Wien, 

 45. 1882 ; Hatschek, Arb. Zool. Inst. Wien, iv. 1882 ; Id. Z. A. vii. 1884. 



Oviposition, Milnes Marshall, Journal of Anat. and Physiol. x. 1876. 



