9 
6 Observations upon the Habits, Structure and | January, 
These folds are hollow and have been thought, until quite 
recently, to have an opening at either extremity, but Prof. Ray Lan- 
kester denies! that there are any such openings, and I have failed to 
obtain any evidence from my specimens that any such apertures 
exist. With the exception of these side-folds and the mouth 
tentacles, the integument presents no appendages whatsoever. Ex- 
ternal sense-organs are also wanting, except upon the left side of 
the body near the anterior end of the chorda dorsalis, where 
a small ciliated pit is said to be located which it is claimed, by 
Kölliker? its discoverer, and others, represents a nasal depression, 
or cavity. I have not been able to make out this pit, and even if 
it is present, it is probable, that these animals gain their impres- 
sions of external objects entirely by the general sense of touch. 
The adults, while varying somewhat in size, as is the case with 
most adult animals, do not differ very much otherwise in general 
appearance except during the breeding season, when the female 
becomes filled with ova, and the abdominal portion becomes, in 
consequence, much larger than ordinary. At this period the ova 
show very plainly as a row of large white spots along either side 
of the animal, Fig. 1, Pl. 1, but at other times, and in the males, 
there are no such spots visible to the naked eye. These differ- 
ences of size and sexual appearance were well marked in my 
specimens, for while they varied in length from Iygth to ryeth 
inches, thus being of rather small size, the female, which was the 
largest, was so distended with ova that her body was much 
- rounder, and consequently more opaque in appearance than the 
bodies of the thinner males. The young, Fig. 5, Pl. 1, and 
Fig. 7, Pl. m, resemble the adults very much in outline, but differ 
in many points of structure, which will be noticed in treating of 
their development, and in being quite transparent, looking much _ 
like animated bits of isinglass when in the water. This trans- 
parency, however, gradually gives place, as they grow old, toa _ 
semi-opaque condition which permits the outline of different parts — 
to be made out, but not with any great degree of distinctness 
unless under a very strong light, and the older and larger the speci- 
men, as a matter of course, the less the distinctness. The young — 
specimens varied in length from {th to 7th of an inch, although 
_ the greater number were about th of an inch long. 3 
; 1 On some new points in the structure of Amphioxus. Prof. E. Ray Lankester. a 
Quar. Jour. of Micro. Science. Vol. 15, p. 257, 1875. ee Me 
? Miiller’s Arkiv, p. 32. Berlin, 1843. 
