Publisher's Synopsis
Excerpt from Contribution to the Embryology and Phylogeny of the Pycnogonids, Vol. 5: A Dissertation, Presented to the Board of University Studies for the Degree of Doctor of Philosophy
Then Prof. Dohrn attempted the solution from the standpoint of Embryology, instituting a comparison "or even identity" between the Pycnogonid larva and the Nauplius, believing the Pycnogonids to have diverged from the Crustacea at this point. During the following tventy: five years opinions once more vacillated between Arachnidan and Crustacean affinities. Recently Prof. Dohrn and Dr. Hoek have each independently monographed the group, placing the morphology of the order on a very firm basis. Independently likewise they each reached the conclusion that the group is to be placed neither with the Arachnids nor with the Crustacea, but that these three groups have come down in parallel lines.
The early stages of the embryology of the Sea-Spiders have been practically untouched, and before any final decision as to the affinities of the group is to be made, these stages in the development should be known and take equal rank with Comparative Anatomy in disentangling the relationships of the group.
For many reasons the present paper attempts in no way to give a complete answer from the embryological side. The very great difficulties of a suitable technique had slowly to be overcome, and the time at command prevented a detailed description of the different organs arising from the germ-layers, so that much remains that might be done.
In the summer of 1889 material for work was collected at Wood's Holl, Mass. Through the courtesy of Prof. MacDonald I was enabled to collect and study at the station of the U.S. Fish Commission at this place. To Prof. MacDonald I am also indebted for many other kindnesses extended during my stay at Wood's Holl. Three genera of Pycnogonids, each with a single species, are to be found at this place, viz. Pallene empusa, Phoxichilidium maxillare, Smith (Anoplodactylus lentus, Wilson), and Tanystylum orbiculare. During July, August and September these are found with eggs. Pallene inhabits the hydroids (Tubularia, Pennaria) on the piles of the wharves, and is also common on the red sea-weeds below low-tide mark. The hydroids or sea-weeds as soon as collected were brought into the laboratory and worked over piece by piece.
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