IV. On the Mitraria Larva of Owenia fusiformis Delle Chiaje

This work is the outcome partly of a suggestion made by Dr. E. J. Allen that the Mitraria larva might prove a fruitful subject for investigation, and partly from an interest in this creature aroused during student days when collecting at Port Erin and Millport. These hopes have been amply fulfilled, and as a result this paper is offered as a contribution towards the biology of one of the strangest of sea creatures. The chief interest centres around the metamorphosis, cataclysmic in its rapidity and astonishing in the profound changes it brings about within a few seconds. In this respect a few other larvae resemble it, the most familiar of them being the Actinotrocha, and more especially the endo-larva ofPolygordius lacteus , so fully and carefully described by Woltereck (1902). Throughout the following pages frequent comparison will be made with thisPolygordius larva, and it should be understood that unless otherwise stated, a reference toPolygordius means to the endo-larva ofP. lacteus .