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portion of the lateral line thins out and ultimately it is quite impos- 
sible to find it in sections. But probably it never really disappears but 
persists throughout life as a connexion between the individual sense 
organs. In Adult Teleostei according to Bodenstein and Solger 
such a connexion exists, and Solger says that »In der That eine ner- 
vöse Verbindung der Einzelorgane zu einer Organkette vorliegt.« Such 
»Verbindung« is I believe brought about by the persistence of the cord 
of cells which as shown above connects the sense organs of the lateral 
line in their development. 
The development of a sense bulb from one .of the segmental 
thickenings takes place in the following manner. Certain of those cells 
of the thickening which are next the outer surface, lengthen until 
they reach the surface of the body, and acquire terminal hairs. The 
remaining cells arrange themselves around the base of these cells as à 
centre. 
Shortly after the lateral line has commenced to form from the 
epiblast, the lateral nerve arises as a branch of the vagus, taking its 
origin from the ganglion of the vagus. I have not observed the very 
first origin of this nerve, in the earliest stage I possess it is already 
a well marked nerve and is found in several transverse sections. 
It grows backwards along the whole length of the body following the 
course of the lateral line. At its origin it is situated far from the epi- 
blast, but as it grows backwards it approaches the skin and comes 
to lie between the two muscle plates just under the epiblast. But it is 
everywhere separated from the epiblast and the lateral line by the 
cuticular basement membrane of the epidermis. In the neighbourhood 
of the ganglion of the vagus the lateral nerve is a nerve of fairly con- 
siderable thickness, but as it approaches the epiblast it becomes much 
thinner and difficult to follow. Its growing point is somewhat abrupt, 
and at this place as elsewhere it is not fused with the lateral line. Im- 
deed here as everywhere else it is separated from the lateral line by 
the cuticular basement membrane of the epidermis. In fine, at no 
period of its development does the lateral nerve of S. fario lie within 
the epidermis. 
With regard to the later history of the organs and nerve there 
remains but little to add. At the time of hatching the sense organs 
consist of a number of bulbs lying on the free surface of the epidermis. 
The connexion between neighbouring organs which in the early stages 
is so well marked a feature is no longer obvious. But I believe it still 
persists. As long as the young S. fario possesses yolk the sense bulbs 
still lie free on the surface. But about the time at which the yolk is 
entirely used up, viz. when the young are three months hatched, the 
