Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 CKUSTACKA. 4To The males are smaller, sometimes even dwarfed, and then attached to the females like parasites. They almost always possess appa- ratuses for holding the females and for transferring the spcrmato- phores during copulation. The larger females, on the other hand, frequently carry the eggs about with them in sacs, the membranes of which are secreted by the so-called cement glands. Development takes place either directly or by
Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 CKUSTACKA. 4To The males are smaller, sometimes even dwarfed, and then attached to the females like parasites. They almost always possess appa- ratuses for holding the females and for transferring the spcrmato- phores during copulation. The larger females, on the other hand, frequently carry the eggs about with them in sacs, the membranes of which are secreted by the so-called cement glands. Development takes place either directly or by metamorphosis. The metamorphosis is sometimes retrogressive. When the develop- ment is direct, the young animals, on leaving the egg, already have the body form of the adult. The larva known as the Naujylius (fig. 332) is of great importance as a point of departure. This larva possesses an oval body, on the ventral side of which are present three pairs of appendages for the sense of taste, the prehension of food, and for locomotion. These appendages correspond to the two pairs of antennaj and mandibles respectively. Parthenogenesis is said to occur in certain gi-oups {P/ii/llo- poda). Almost all Crustacea are carnivorous. Some of them suck the juices of living animals on which they are parasitic. For the systematic review of this heterogeneous group, it is convenient to divide the numerous orders into two series. 1. The small simply organized Crus- „ „„„ xr ,• , ^ •' tj Fig. 332.—Nauplms larva of tacea, the number and form of whose Baiamn, seen from the side. appendages is very various, will be in- 1«T 'ioXS,.'; eluded as EntomOStraCa (0. Fr. Mliller). (second antenna) ; , third To this group belong the orders Phyllo- 7w^tp^b^m^^! °*' pc<la, Ostracoda, Copepoda, and Cirripedia. 2. The higher Crustacea, characterised by a definite number of segments and appendages, may be grouped together as Malacostraca (Aristotle). In this group are included the order
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