LANOELET. 
1221 
The Lancelet attains in Scandinavia a length of 
about V 2 dm. Lilljeborg’s largest specimens were 52 
mm. long. According to Carus it sometimes mea- 
sures at least 70 or even 100 mm. a During life the 
body is of a jelly-like transparency; through the skin 
and muscles may be perceived the light green notochord, 
the somewhat darker c tecum, and the stomach with 
intestine, the last-mentioned organs more or less dark 
according to the nature of their contents. In a certain 
light the skin appears somewhat iridescent, and a hand- 
some appearance, as of a row of white, transparent 
rings, is presented by the plate- like rudimentary fin- 
rays. When the seminal or ovarial sacs are full, they 
are perceivable on each side as a series of white or 
green globules, the green egg-sacs each with a dark dot. 
The habits of the Lancelet have been sketched 
above. Its breeding-time lasts throughout the summer; 
but in wet and chilly weather it does not spawn. 
Theel obtained at the beginning of July a large number 
of specimens which were placed in the aquaria of Kris- 
tineberg and laid eggs that developed normally. At 
Haugesund in Norway Lilljeborg received at the be- 
ginning of August specimens not yet quite ripe. On 
the west coast of France and in the Mediterranean the 
Lancelet commences spawning in March. According to 
Hatschek, as well as Ray Lankester and Willey, 
who made their observations in the well-known lagoon 
of Pontano, near Messina, the spawning always takes 
place in the evening, segmentation commencing between 
7 and 8 p. m. At 11, say the latter writers, the 
gastrula begins to develop, and at 1 a. m. it is com- 
plete. At 3 a. m. it begins to revolve by cilia within 
the egg-membrane, and at 5 a. m. it already has two 
pairs of myocoelomic pouches, when it bursts the egg- 
membrane and becomes free-swimming. Thirty-six 
hours after the commencement of segmentation the 
embryo has acquired a mouth and a rudimentary gill- 
slit. Soon afterwards the anus opens, and the larval 
period now begins. The larva; swim both at the sur- 
face, where Malm found them off Gasd Island (Bohus- 
]&n), and deeper down, at a depth of 15 — 20 fthrns., 
according to Ray Lankester and Willey. Here they 
are found in countless myriads together with other 
minute marine creatures ( Noctilucce , Beroe, Sagittce, 
Calani ) and their larvae, amongst that mass (Hensen’s 
plankton ) which the Norwegians call Aat b . The deve- 
lopment of the larva progresses much more slowly than 
that of the embryo. A fortnight is said to elapse be- 
fore the formation of the second gill-cleft; and the 
remainder of the development, until the atrium is 
complete, and the Lancelet begins to bury itself in 
sand or mud, is said to take months (Hatschek). The 
course of the development is besides very irregular, 
and it may be so protracted, at least in the North, 
that Dr. C. W. Aurivillius found larvae 5 mm. long 
swimming freely at a depth of 15 — 30 m. below the 
surface of Gullmar Fjord, in the middle of November. 
In its hiding-place at the bottom the Lancelet 
leads the life of the worms, and to escape danger it 
buries itself deeper down, for Malm remarks that, un- 
less the dredge — the instrument most generally em- 
ployed in the capture of marine animals at the bottom 
— takes a sufficient hold in the gravel, sand, or mud, 
there is little hope, even in places known to be fre- 
quented by the Lancelet, of securing a single specimen. 
Few fishes are so tenacious of life; and even if the 
body be cut into pieces, the ciliary motion does not 
cease at once in the severed parts. In salt water 
changed from time to time, it may be kept alive for 
months; and Lilljeborg relates that a number of Lan- 
celets which he had dredged up at Haugesund on the 
2nd of August, in a quantity of shellsand, and thrown 
on the dry rock, were alive three days afterwards, 
though the moisture of the sand was not very great, 
and though rain had fallen in the interval. In spite 
of the sluggish life it usually leads, the Lancelet is 
quick of movement when disturbed, wriggling about 
in the aquarium like a young Eel, but with either end 
foremost. Its endurance is not great, however; if the 
observer should desire to induce the captive to lie still 
for examination, it may easily be tired out, and it 
will then suffer itself without more ado to be conveyed 
where a closer view may be obtained, provided only 
that it has no soft bottom in which to hide itself. In 
the day-time it lies motionless. At night it moves 
about; but if a light be brought near the aquarium, 
it hastens to conceal itself. As human food it is worth- 
less; but it has enemies, no doubt, in plenty. 
“ Carus, however, combines this species with the Pacific Branchiostoma , and his account of Lancelots 1 dm. long may perhaps de- 
pend on that fact. 
b See above, pp. 970, 971. 
c Bih. Vet. Akad. Hand!., Bd 20, Afd. IV, No. 3, p. 11. 
