180 
ANIMAL PEDIGREES. 
Aug., 1891. 
Figs. 8 to 10.—Young and adult specimens of one of the swim¬ 
ming Crabs (Portunus), to illustrate the transition from the long¬ 
tailed to the short-tailed condition, 
Fig. 8.—The Zoea stage, characterised by the great length of the 
spines on the cephalothorax; by the large size of the powerful 
rowing maxillipedes ; and by the long, jointed tail. The larva is 
swimming in the direction of the long dorsal spine, the spines 
serving to guide its course. (After Weldon.) X 15. 
Fig. 9.—The Megalopa stage. This is the typical Macrurous 
condition, comparable to that of an adult Lobster or Prawn. (After 
Claus.) X 5. 
Fig. 10.—The adult Crab. As compared with the Megalopa stage 
the cephalothorax has increased greatly in width, while the tail 
has become relatively smaller, and is carried turned forwards 
beneath the thorax. (After Bell.) X 
Figs. 11 to 14.—Young and adult specimens of Sacculina, to 
illustrate the Degeneration or Retrograde Metamorphosis which the 
parasite undergoes in the course of its development. 
Fig. 11.—The Nauplius stage, in which the young Sacculina 
hatches. The three pairs of appendages correspond to the antennules, 
antennae, and mandibles of a Crab or Crayfish. The black spot 
between the antennules is the eye, and the small patch immediately 
behind the eye and between the two hinder pairs of appendages is 
the ovary, which is already present at this very early stage. Unlike 
the Nauplius stage of other groups of Crustacea the Sacculina 
Nauplius has no mouth or alimentary canal. (After Delage.) x 90. 
Fig. 12.—The Cypris or pupa stage. It is at this stage that the 
young Sacculina, hitherto a free swimming animal, attaches itself 
to a Crab and becomes parasitic. The pupa is characterised by the 
bivalved carapace ; the stout antennules by which it fixes itself 
to the Crab ; and the six pairs of locomotor appendages. The black 
spot is the Nauplius eye, and the mass immediately below it is the 
ovary. (After Delage.) X 90. 
Fig. 18.—The Sacculina three days after fixing itself to the Crab. 
The six pairs of swimming legs have rotted away and fallen off; the 
bivalved carapace is being detached, and is carrying with it the eye 
and certain debris from the body. The sole parts remaining, out of 
which the adult Sacculina will be formed, are the antennules, now 
modified into a tube, which is represented projecting through a piece 
of the skin of the Crab ; and the head, which forms a bottle-shaped 
mass attached to the tube, and containing the ovary. (After 
Delage.) X 90. 
Fig. 14.—Adult Sacculina attached to the ventral surface of the 
tail of a Crab (Portunus). The Sacculina is the large dark-coloured 
bag in the lower part of the figure ; it is attached to the Crab by a 
short fleshy stalk, not seen in the figure, which, penetrating the skin, 
spreads out into a tuft of branching roots in the Crab’s body. (From 
nature.) X 
Figs. 15 to 18.—Stages in the development of the common Frog, 
Kana temporaria. (From nature.) 
Fig, 15.—The egg. X 3. 
Fig. 16.—The Tadpole *at the time of hatching. The mouth is 
not yet formed, the Tadpole being still dependent on the food yolk 
present in its body. Two pairs of external gills are present as 
branched finger-like processes at the sides of the neck. Below and 
in front of these is the horse-shoe shaped sucker by which the 
Tadpole fixes itself, and at the sides of the front of the head the rudi¬ 
ments of the nose and eye are seen. X 3. 
