BUDDING- PROCESSES OF CEPHAL0D1SCUS DODECALOPHUS. 511 



aud food-currents, hence it is certain that the chordate pharynx and allied organs have 

 arisen, and have reached a complexity as high as that of Amphioxus, under these con- 

 ditions. In this category may be included the notochord (or pleurochords), pharyngeal 

 clefts, endostyle, sub-neural gland and the hyper-pharyngeal groove of Amphioxus, 

 which are intimately connected with the vertebral column, gill-slits, and visceral arches, 

 thyroid gland, hypophysis and sub-notochordal rod respectively, in the true Vertebrata. 

 Assuming that the pharynx of the earliest archi -chordate was homogeneous, and that 

 the return water-current from the oesophagus took a dorsal course along grooves formed 

 by the continuity of the current, then the epithelial cells lining these grooves would lose 

 their secretory power, and might easily undergo a chordoid degeneration, which, serving 

 as an efficient means for keeping open the cloacal grooves, would become permanent, and 

 the pleurochords would become established. The paired condition may be primitive or 

 secondarily acquired in the Diplochorda. 



The Gonads. 



Both Professor M'Intosh (4) and Dr Harmer (l) have figured and alluded to the 

 ovaries and oviducts of Cephalodiscus and to their descriptions. I have little to add. 

 I have been equally unsuccessful with them in the search for male elements. In one 

 preparation of part of the ccenoecium there appears a dense cloud of minute, darkly- 

 staining oval bodies, which might possibly be interpreted as free spermatozoa ; but it is 

 fairly certain that the colony obtained by the Challenger is " female " throughout. In 

 a series of sections in the horizontal longitudinal plane, the oviducts and ovaries are 

 cut nearly transversely, though at an angle. 



In fig. 10, the left side shows the opening of the oviduct to the exterior, as a slight 

 cup-shaped invagination of the ectodermal cells. On the right side, the oviduct (g.d.) is 

 cut rather further back, and the cells are here seen to be longer, with their nuclei more 

 irregularly arranged than is the case with the ectoderm. The oviduct is covered on the 

 inner side by the wall of the ccelome, which is here rather thicker than elsewhere. In 

 fig. 1 1 the dorsal mesentery is observed to give out a lateral mesentery on each side to 

 the base of the oviduct. On the right hand of this figure the oviduct is free from 

 the ectoderm, and is seen to be supported by the lateral mesentery. Here the oviduct 

 has a fine lumen, with indications of cilia. The epithelial cells show masses of black 

 pigment, chiefly at their inner ends. 



Fig. 12 gives two views of the junction of the oviduct (g.d.) with the ovary (ov.). 

 On the left side the cells of the oviduct, with their abundant pigment, can be observed 

 almost encircling the lumen of the ovary, whilst, especially on the inner side, the wall 

 of the ovary can be recognised. On the right the oviduct is represented by a mere 

 segment, whilst the greater part of the section is occupied by the reticular tissue of the 

 ovary. 



