TL;DR: The results of more than 30 years field observations and research work carried out from the Isefjord Laboratory, Vellerup Vig (Zealand, Denmark), which is owned and financed by the author, are represented.
TL;DR: An overview is presented of non-indigenous marine and estuarine plant and animal species recorded from The Netherlands, both exotic species from outside NW Europe and non-Indigenous species from elsewhere in NW Europe.
TL;DR: A re-examination of the type material of Eudendrium elsaeoswaldae Stechow, 1921 revealed that it is conspecific with E. ramosum and newly collected material from the type locality confirmed this.
TL;DR: The hypothesis that medusa reduction has happened repeatedly in the family Hydractiniidae is supported, thereby calling into question the tradition of hydroid taxonomy which defines genera based on degree of medusa Reduction.