196 
from the exterior into the archenteron. While all other 
tube in lower Chordates has its starting point at the blas- 
topore and proceeds in a forward direction. Characteristic: 
of the stomodaeum, at least in young stages, is the dense 
coat of cilia which induces a current of water. In Am- 
phioxus the neural tube is also clothed with cilia, equally 
producing a water current from in front backwards (HAT- 
SCHEK, 1882, p. 59, 71) and in higher Chordates a fine coat 
p.card. 
stom. 
can. med. 
Fig. 3. (cf. fig. 11). Diagram representing the derivation of a 
Chordate (Acraniate) from an Annelid (the Annelid is placed 
with the ventral side up). 
an. med. medullary canal, 7. mouth, zeur. p. neuropore, 
p. card. cardiac pore, p. tkn ebi pore, stom. stomo- 
daeum. 1, 2, 3, mesoderm se 
The a be has a Mather. colour than the ectoderm. 
of cilia is often observable covering the ependyme of the 
neural tube or the neural plate. Thus MORGAN (1890) remarks :. 
“MR. WIGHTMAN has demonstrated to me in the neural tube- 
medullary tube is almost complete if only we assume tha 
n Chordates the former has become very long and has- 
xtended over the whole length of the body, carrying the 
Barcin pore backwards to the hinder end where we find 
it now as the neurenteric canal. In the last chapter we 
