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Fig. 24. 
N Ometh e 
Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. 
embryos from this time forward until they attain the length of over 30 mm. 
The atrium is completely obscured by the bulbus and ventricle (V.). The 
septum transversum (S.trans.) reaches completely across from side to side of 
the body cavity. The right and left lobes of the liver (L.) are now of almost 
equal size and extend posteriorly to the first turn of the spiral valve. The 
median or connecting lobe of the liver is somewhat broader than indicated 
in the figure, as it is obscured in part by the vitelline duct (D.vit.). Below 
and to the left of the vitelline duct is the ventral portion of the pancreas, 
which now lies in a notch in the left lobe of the liver, and which shows 
slight secondary lobulations. The spiral valve (Sp.v.) makes thirteen turns. The 
digitiform gland (Dig.gl.) is a prominent finger-like process extending forward - 
from the right side of the gut near its dorsal surface. Immediately behind 
the digitiform gland the intestine is somewhat constricted. The cloacal plate 
now appears as an oval depression bounded on either side by low rounded 
ridges. 
Dissection of an embryo 28 mm. in length corresponding with normal plate series 
N0.0292 %X6. 
In this embryo the nasal flaps are beginning to develop. The median, 
ethmoid and pre-oral canals (On.m., Cn.eth., On.pre.-0.) are visiable, and long 
gill filaments project from all of the gill slits. The heart is similar in shape 
to that of the preceding dissection. The lateral lobes of the liver now 
extend posteriorly to the third turn of the spiral valve, and the inequality 
in size which characterized these structures in the younger embryos is now 
absent. Anterior to the vitelline duct, which is turned somewhat backward 
in the dissection, is seen a small projection which extends posteriorly 
from the connecting median portion of the liver. Posteriorly and to the 
left of the vitelline duct is the duct and ventral lobe or head of the pancreas 
(Pane.). Fourteen turns of the spiral valve (Sp.v.) are present, the adult 
number now having been attained. The great diameter of the middle 
portion of the intestine as compared with its posterior and anterior extremities 
is noticeable in this embryo, and is characteristic of this and succeeding 
stages. The subintestinal vein (V.sub-int.) extends along the ventral surface 
of the intestine, slightly to the left of the median line. The digitiform 
gland (Dig.gl.) now arises far posterior to the last turn of the spiral valve. 
It is much elongated, and lies completely on the right side of the intestine. 
The cloacal plate (Ol.p.) which is seen in part in side view, differs but little 
from that seen in the preceding dissection. 
Fig. 25. Dissection of an embryo 34 mm. in length, corresponding to normal plate series No. 31. >26, 
In this embryo the lateral and mesial chambers of the nasal pits (N.p.) are almost separated externally 
by the nasal valves. There is a distinct ventral border to the rostral plate (R.pl.) and the ethmoid (On.eth.), 
