27 
<tonsi(lerably from the other species in its liahits. Tlie six- 
letf^ed larvm of Pj’cnogonum attach themselves to the base 
of the poh'pes of (lava muJticornis (Forskal) and pierce the 
cuticle by means of the proboscis, which is inserted into 
the host. I'he period of parasitic life, during which there 
are several moults, is much longer than in Anaphia. It is 
interesting to note that the proboscis of the larva becomes 
moditied for this mode of life, as during the moults it grows 
longer and becomes curved downwards and inwards, having 
the form of a long tube, quite diherent from the proboscis 
of the six-legged larva and of the adult. In the last stage 
observed the young has all the appendages of the six-legged 
larva, two pairs of ambulatory legs well developed, and the 
thiid pair are represented by short outgrowths. When this 
stage begins to moult the contents of the first three pairs 
of appendages aie drawn into the body, leaving no signs of 
their previous existence; and the cuticle of the third pair 
of ambulatoiy legs contains these limbs fully developed with 
<daws. It is evident that after this moult the larva becomes 
a young I’ycnogonum, differing from the adult only in the 
absence of the fourth pair of ambulatory legs. As such a 
stage has previously been observed in a free living condi- 
tion,* we may assume that the life-history of Pycnogonum 
is now fully known. Its most (diaracteristic feature is its 
ectoparasitic mode of life in the laival stages. 
I take this opportunity of expressing my sincere thanks 
to Professor .Meek and Mr. Storrow for their kindness and 
assistance. 
Lately observed by myself at .Millport. 
