1880. | Development of Amphioxus Lanceolatus. 19 
EXPLANATION OF PLATE I. 
The full length figures were drawn either from careful measurement of the parts 
of the animals, or with the assistance of a camera, so that the outlines may be con- 
sidered as very nearly, if not quite, correct. Under each of these figures is a line 
aaa the length of the individual. 
Fic 
dult female, 1,’;ths inches in length, seen from the left side. The egg- 
cases are represented as squarish blocks attached beneath the body-muscles 
within the limits of the ETE which is almost fully expanded. The 
beraikin clefts are shown as oblique lines crossing the anterior portion of the 
pharynx. In this figure the anal opening is represented about ły of an inch too 
far back, and, for want of space to make the lines clear and distinct throughout 
their entire length, the full number of muscle-plates at the ends of the body 
have not been indicated. ; 
—The prana ae tae fr ee a its gem and a portion of the 
Petirke 2: ring shows the divisions of. 
gach into segments: an sa the ba on Socios of “a ten tacular Eper gation 
3-— of the right side of a portion of the pharynx, showing the extent ind 
pon nut the sa cpa liver ne kage slender eel esr or nade which attach it 
the: Dari of the branchial a 
` ketika of the branchial dor of the left side, viol ing the central sare 
with their central division lines; the extent of the op s in the length of ea 
arch; the pa lining p tia the triangular spaces, æ, between the bases a 
the arches which a med the “branchial yas ” of the blood system, 
and the cro be b run a fi rom one side of the arches to the other, and acting 
as stiffeners. to the e'caniilaginous framew “iri 
FiG.5. —Young animal, 3,ds of an inch i gth. The uth apertur 
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Fie. 
e is 
eccentric opening upon the left side ak Partially nia 2 the forming 
tentacles. The branchial arches are large and prominent, and seven in numb 
and the liver caecum is just forming from the aa portion of the ali peer 
Gaal 
EXPLANATION OF PLATE II. 
. 
i ERr frer of the anterior portion of the body of a young Amphioxus, show- 
ing the ix pharyngeal o penings, the first three openings for the left. bran- 
chial e par the mouth-cavity as it appears shortly after the cleft from the 
pharyngeal mouth aperture to the ciliated pit has closed. The peculiar shape of | 
the anterior pharyngeal Eemia is caused by their position na the right side 
at the median line of the phar 
—An eo _ of the same portion of the body shown in Fi gi re the 
OR un aper ure, the ciliated mouth cavity, and the cleft. Jiane 
the two ee re plainly i 
ated. 
. 3-—Portion of the- RENEA canal of a young animal parry the last bran- 
chial opening, upon the left side of the payes, and the entire stomach cavity, 
and show h the ventral blood vessel conform- 
ing to its lowes border 
IG. 4.—An egg capsule with its quota of ova, very much en larged, , 
. 5.—Diagrammatic cross-section of the body of a young Amphioxus. Sectio; 
m the phary of t 
y 
ade through the pharyngeal mouth aperture and one of the pharyngeal clefts, 
7, to show the connection of these openin th the ce 
The point ate the wall or mouth welt, just to the right of the letter æ in 
processes = of The mout 
6.—View of a portion of. Me muscular system of the left slide of the body of an © 
adult, showing the disk-like character of i notochord ; the muscle-plates of pa : 
side muscles; the distribution x = nerv a bad si en and the attachment and 
form of the generative bodies 
ordinary a 
- 7-—Young animal, {ths of an fon in agit, ca ing pharyngeal mouth open- — 
ing with seth $ entlaginos pear-shaped welt; ciliated pit, and the first three 
pharyngeal openings. 
