. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). 3 r 404 IN VERTEBRATE MORPHOLOG Y. and is known as the telson. All these segments with the exception of the telson, and in the Leptostraca of the seg- ment immediately in front of it, bear appendages. Folds of the integument forming a eephalothoracic carapace are fre- quently present, but it is rare that a bivalved shell occurs. The stomach is always provided with chitinous tteth and forms an efficient masticatory organ, and lateral eyes are present except in some Cumac
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). 3 r 404 IN VERTEBRATE MORPHOLOG Y. and is known as the telson. All these segments with the exception of the telson, and in the Leptostraca of the seg- ment immediately in front of it, bear appendages. Folds of the integument forming a eephalothoracic carapace are fre- quently present, but it is rare that a bivalved shell occurs. The stomach is always provided with chitinous tteth and forms an efficient masticatory organ, and lateral eyes are present except in some Cumacea and in some forms belong- ing to other groups which inhabit caves or the depths of the ocean, under which conditions the eyes become rudimentary. The openings of the female reproductive organs are always situated on the basal joints of the appendages of the sixth thoracic segment, and the male openings on the appendages of the eighth segment. The antennary gland is usually well developed, while the shell-gland is either rudimentary or wanting in the adult. Although numerous rather small forms belong to this class, yet on the whole they much surpass in size the Ento- mostraca, some forms even reaching a length of over 50 cm. A few forms, such as Euphamia and Fenams, leave the egg as a Nauplius, but in the majority this stage is passed before hatching, the embryo first leading a free existence at a later Btage in the larval form known as the Zijea, though in some cases hatching may be retarded until later stages, in fact sometimes until the adult form is acquired. I. Subclass Leptostraca. The Leptostraca are exceedingly interesting forms, present- ing similarities to the Entomostraca on the one hand and to the Malacostraca on the other, thus connecting the two classes. They are exclusively marine in habitat and possess a, thin bivalved shell-duplicature which is provided with an adductor muscle and is prolonged in front into an unpaired plate which covers the dorsal surface
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