CIHE1PEDIA. 



443 



lum ornatum and Ilia Cuminyii; also with the remarkable genera 

 Cryptopkialu& and Alette (fig. 350). The males of these forms are 

 not only small and dwarfed, but also, according to Darwin, have 

 neither mouth, digestive canal, nor thoracic appendages. As a rule, 

 two or sometimes more attach themselves to the body of the female. 



Development. The eggs, while still within the brood-pouch, 

 undergo an irregular segmentation. The clear cells arrange them- 

 selves around the food yolk in the form of a blastoderm, the ventral 

 side of which soon becomes considerably thickened in consequence of 

 the appearance of the mesodermic layer. The larvee leave the egg 

 as Nauplii (fig. 351, a, 6), of oval or 

 pear-shaped form, with unpaired 

 frontal eye, lateral frontal horns, 

 and three pairs of appendages, of 

 which the anterior is simple, the 

 two next biramous and closely beset 

 with swimming setaj. 



After several moults, the larva, 



which has grown to a considerable 

 size, enters on a new stage of de-' 

 velopment, the so-called Cypris stage 

 (pupa) (fig. 352). The reduplica- 

 ture of the skin has the form of a 

 bivalve mussel-like shell, through 

 the gaping ventral edges of which 

 the appendages can .be protruded. 

 While the form of the shell recalls 

 that of the Ostracoda, the structure 

 of the body, so far as the segmenta- 

 tion and form of the appendages are 

 concerned, approximates to that of 

 the Copepoda. The anterior ap- 

 pendage of the Nanplius larva has 

 given rise to a four- jointed antenna, 

 the penultimate joint of which 

 has become large and disc-shaped and contains the opening of the 

 cement gland, while the terminal joint bears in addition to tactile 

 seta? one or two delicate lancet-shaped olfactory hairs. The frontal 

 horns are transformed into two conical prominences near the an- 

 terior margin. Of the two pairs of biramous appendages, tho^e 

 which correspond to the second pair of antennaB arc cast ofT, while 



FIG. 352. Median section through a 

 pupa of Lepas. A' Attaching antenna 

 C, carina ; Te, tergum ; Sc, scutum 

 Ov, ovary ; G, cerebral ganglion 

 Gg, ganglionic chain; D, alinientarj 

 canal ; Cd, cement gland ; Mk, oral 

 cone ; Ah, abdomen ; P, rudiment of 

 the penis ; M, muscle. 



