THE LARVA OF FHOXICHILIDIUM. 



155 



considerable degeneration before passing into that of the adult. 

 This is connected with its parasitic manner of life. 



On leaving the egg, the larva of Phoxichilidium possesses on the 

 whole the organisation of the usual sixdimbed Pantopodan larva, 

 but is distinguished from the latter by the fact that the usually 

 hookdike terminal joints of the two posterior pairs of limbs are 



Fig. 73. — Various larval stages of Phoxichilidium, (after Dohrn, Semper, and Adlerz). A, 

 free larva with the tendril-like flagellae on the two posterior pairs of limbs (77 and 777). 

 B-D, larval stages found in Hydroid polyps. (A is more highly magnified than the other 

 figures.) 7-777, limbs ; d, intestine with its caeca ; dr, glands of the first limb ; h, larval 

 integument in the act of becoming detached ; n, ventral chain of ganglia ; s, proboscis. 



much lengthened, and form long flagellae, which can coil up like 

 tendrils (Fig. 73 .4). These flagellae, which may be much longer 

 than those represented in Fig. 73 (e.g., in Phoxichilidium femoratum, 

 (Hoek)), are probably used for attachment, the larvae winding them 

 round the Hydroids (e.g., Hydractinia, Podocoryne, Tuhularia, 



