Northern Hydroida in the Collections of the Rijksmuseum van Natuurlijke Historie and the Zoological Museum at Amsterdam, with Notes on their Distribution

In the course of 1941 I studied a great number of Hydroida from various northern localities present in the collections of the Zoological Museum at Amsterdam. Most of these collections were made by trawlers from IJmuiden and for the greater part presented to the Museum by Mr. F. P. Vermeulen. They are from localities which are accurately known. Moreover, several samples of Hydroida are present in those collections, which were taken in the neighbourhood of Iceland, either by trawlers from IJmuiden or by Dr. J. Metzelaar and Dr. H. Engel. They were all sent to Dr. P. L. Kramp in 1938, who examined them for his list of Hydroida in "The Zoology of Iceland", vol. 2, pt. 5a. Most of these samples returned identified, but some bottles were returned unnamed from the Zoological Museum at Copenhagen. They contained several interesting species, some of which are not mentioned in Kramp's list. Only one sample contained some dried specimens, nevertheless in good condition (Iceland, near the south coast, 100 fms., J. Metzelaar and H. Engel, July, 1920). They were softened for determination and are now preserved in alcohol. In addition to these Hydroida I studied several samples of Hydroida from corresponding localities present in the collections of the Rijksmuseum van Natuurlijke Historie at Leiden. One of these samples is of great interest, viz., the Hydroida collected near Waigatsch on August 17, 1882 by J. Mar. Ruys. These Hydroida were presented to the Rijksmuseum van Natuurlijke Historie by Prof. Dr. H. J. Lam. the director of the Rijksherbarium at Leiden, they had been sorted out of the collections of this institution by Miss Dr. Jos. Th. Koster, custodian of the algae of the Rijksherbarium from among plants collected near the same locality.