400 
E. BAY LANKESTER. 
important diagrams of Hatschek, which are reproduced side by 
side with them. 
A curiously modified tract of connective substance is to be 
observed forming that part of the notochordal sheath which is 
attached to the dorsal wall of the pharynx (PI. XXXVI .<4, 
fig. 1 x.). It has an irregular granular appearance, quite dis- 
tinct from that of the connective substance in any other 
region, excepting a similar tract on the upper median surface 
of the notochordal sheath ( y . in same figure). 
The reticular tissue with nuclei which forms the axis of the 
furcal portions of the primary bars in the endostylar region of 
the pharynx seems to be distinct in character from all the other 
skeletal tissues of Amphioxus (PI. XXXVI B, figs. 4 to 9). 
The Notochordal Tissue.— The series of vertical laminae 
which build up the notochord of Amphioxus have often been 
described and figured. I desire here merely to draw attention 
to the disposition of nuclei within the notochord as shown in 
well stained preparations. There are no nuclei in the position 
described by Moreau (15) towards the axis of the notochord ; 
the nuclei are confined to two perfectly definite regions. In a 
transverse section a series is seen lying in a single row near 
the circumference of the notochord, and extending along the 
inferior third of its area. A second smaller group of nuclei is 
seen dorsally on either side of the dorsal intrachordal canal. 
I have already referred to the superior and inferior intra- 
chordal canals. I may again state here that the notochordal 
tissue does not appear to me to form itself any cuticle or 
investing sheath. Such a cuticle may exist in the embryonic 
condition before the connective-tissue sheath is developed, but 
it would be difficult to attribute any part in the formation of 
the adult notochordal sheath to a delicate envelope of the kind, 
owing to the enormous increase in the bulk of the notochord. 
Summary. — The present memoir by no means professes to be 
a monographic treatment of Amphioxus nor even to deal 
exhaustively with parts of the structure of that animal. It 
must be regarded as a contribution to the knowledge of 
Amphioxus, detailing a few new facts, offering evidence towards 
