EMBRYOLOGY OF THE SEA BASS. 
247 
life one or two sense organs are found in tliis region, and it is extremely probable 
tliat they arise trom the dorso-lateral tract. Indeed this is made nearly certain by 
the condition of the anterior end of the tract at the time of hatching (Fig. 132, PI. 
civ). It is here larger than elsewhere, and the cells begin to assume the appearance 
of sense cells, as if a sense organ were going to form in situ as a modification of a 
particular part of the cord. This calls to mind Allis’s paper on the lateral line of 
Amia (2), iu which he describes sense organs originating at various spots along a 
growing cord by local cell proliferation. The significance of this method of multipli- 
cation of sense organs will be discussed after the formation of the lateral line has been 
described. 
The anterior sensory tract is at the time of hatching very short, and just what 
becomes of it I do not know. Nor do I know whether the gill slits, which are subse- 
quently formed, have branchial sense organs. If they have, the organs must be 
extremely inconspicuous compared with the single embryonie organ. 
I think Hoffmann must have seen the branchial sense organ in the embryo of the 
trout, for on page 7 (17, 1883) he gives a wood cut (surface view) in which the organ 
is shown fairly well, though he calls it an embryonic ‘‘ Spritzloch,” Hoffinauu must 
surely be wroug in his statement that there is an embryonic spiracle in the teleost. 
What he figures as such in his sections is the embryonic gill slit, which does not dis- 
appear at all, as he states is the case. 
Lateral line. —As has been said, it is the posterior end of the common sensory fur- 
row which is transformed into the anlage of the lateral line. In Fig. 147 the general 
character of this end is indicated. The furrow is here long, narrow, and (compared 
with the auditory invagination) shallow. Becoming independent on the elosure of 
the auditory sac, the lateral line anlage forms an elongated narrow sac, the opening 
of which is bridged over by the epidermic stratum. Its appearance and position, 
just behind the ear, is shown in Fig. 148, 1. 1. A section through the anterior end 
of the lateral line at this stage is given in Fig. 78, PI. xcvii, 1. 1. 
Once independent of the rest of the furrow, the eavity of the lateral line invagi- 
nation begins to deepen, becoming at the same time uarrrower, while the lining cells 
grow more columnar. Fig. 105, PI. c, represents a section through a stage four 
hours older than Fig. 148 and shows these changes in the character of the lateral line. 
The cavity is sometimes a simple narrow slit as in the “line” on the right side, and 
sometimes it is dilated at the bottom as on the left. At the ends of the lateral line 
the cavity is considerably wider, especially in its upper portion where the lining cells 
become continuous with the surface ectoderm, than in the middle ; on the left side of 
Fig. 105 the section cuts the anterior end of the line. When the section is unbroken 
the continuity of the lateral line cells with the nervous layer of surface ectoderm is 
perfect, as iu the figures. But sometimes the “line” parts from the ectoderm and 
appears in sections as, .at first sight, a closed tube lying on the mesoderm. Examina- 
tion, however, always shows the incomifieteness of the apparent tube. The attach- 
ment to the ectoderm is stronger at the ends than elsewhere, and occasionally the 
“line” will separate from the ectoderm along its length, remaining attached at one or 
both ends. I have mentioned these imperfect sections because it was probably such 
that led Brook (4) to the conclusion that the Wolffian duct splits off from the ecto- 
derm in the Teleosts. As will be seen later, I agree with the majority of investigators 
