Notes on the Life History of Anaphia petiolata 
(Kroyer). 
By 
Marie V. Lebour, M.Sc., 
Assistant Lecturer in Zoology, Leeds University. 
Temporary Naturalist at the Plymouth Laboratory. 
With Figures 1 to 3 in the Text. 
In the early summer of 1915 it was noticed that many medusz brought 
in with the tow-nettings contained larval Pycnogonids in the manubrium 
and at the junction of manubrium and stomach. The medusv specially 
noticed to contain them were Obelia sp., Cosmetira pilosella, Turris 
pileata, Stomotoca dinema and Phialidiwn hemisphericum. By far the 
greater number were in Obelia, although many were in Phialidium 
hemisphericum and Cosmetira pilosella. They were extremely abundant 
in June, after that became scarcer, and finally disappeared by October. 
On examination they were seen to be larval stages of Anaphia petiolata* 
(Kroyer), a Pyecnogonid common in Plymouth Sound. The older larvee 
sometimes were seen to cast their skins, so that the species could be 
easily recognised, although the fourth pair of walking legs were not fully 
developed. This is evidently the species described by Dogiel (1913) as 
Anoplodactylus pygmeus, the life history of which he traces from its first 
entry into the Obelia hydroid to the older stages when it is ready to leave 
its host. The form he refers to as Anoplodactylus petiolatus occurring in 
cysts in Coryne with Phoxichilidium femoratum must be some other 
species, as his figures prove clearly that it differs from A. pygmeus, and 
also the colour is totally different (a bright pink, while the present form 
‘is a pale yellow). Dogiel believes he has proved that Anoplodactylus 
petiolatus and A. pygmeus are different species from the difference in 
their life histories, and it is evident that he is dealing with two different 
species, but his 4. petiolatus cannot be the same as our form, which is 
certainly identical with his A. pygmaeus, and shows that Sars (1891) and 
Norman (1894) were right in regarding A. pygmaeus as the young form 
of A. petiolatus (Kroyer). 
* This is a synonym of Anoplodactylus petiolatus (Kroyer), See Norman, 1908, p. 202. 
