ZOOLOGY FOR MEDICAL STUDENTS CHAP. 



The CIRRI ri.i'iA are a. group of Crustacea which have entirely given 



up the free-living existence, being attached to rocks ; to floating objects, 



. the bodies of other animals, and in correlation with this the bodily 



modified in the adult although here again there is 



nauplius larval stage (Fig. no, A). The nauplius swims about 



iin ,i A .lavs r. dysis takes place accompanied by a considerable 



:orm. It is now (Fig. 110, B) known as a " Cypris " larva 



from' its resemblance to the members of the group Ostracoda (p. 266): 



body is enclosed in a bivalve carapace, and there are six pairs of 



Ab 



A 



FIG. no. 



^ucculina. X about 70. (From Geoffrey Smith in Iht 



nil History, vol. iv.) A.I and Ant, First antenna; A. 2, sec nd antenna; Ab, 

 uti.iti-d cells; F, horn-like projection ; G, glands ; H, tendon ; M, mandible ; 



<<! thoracic legs by the movements of which it swims. The first 

 antenna rarrics a flattened disc upon which opens the duct of a cement 

 -land producing a sticky secretion. When the Cypris larva swims 

 up against a solid object it is apt to adhere to it and it may be observed 

 apparently struggling to free itself, making as it were several steps with 



ky antennae, until at last its attempts cease and it remains fixed 



in position. The cirripede now gradually takes on its adult form. It 



remaii <1 to the solid object by its head end: the body is 



enclosed in a carapace-like fold of skin termed the mantle ; the compound 



.:.<! the six pairs of swimming legs are replaced by much 



