Haeckel was invited to analyse the samples and prepare the report for four groups of organisms collected during the HMS Challenger Expedition. His report on the Siphonophores is in Volume 28 of the report (Report of the Scientific Results of the Voyage Of H.M.S. Challenger during the years 1873-76). This contains 50 images of siphonophores, plus apparently 9 woodcuts (I’ve never been able to locate the latter, but they may be embedded in the text). The plates are available at two sites – the Bossard site is the most accessible; the images on our site have been downloaded from the Heritage Library site, as they are of better quality.
The following description of the Siphonophores is downloaded from a spectacular site on these organisms created and maintained by Dr Casey Dunn of Brown University in Rhode Island
“Siphonophores belong to the Cnidaria, a group of animals that includes the corals, hydroids, and true jellyfish. There are about 175 described species. Some siphonophores are the longest animals in the world, and specimens as long as 40 meters have been found. The majority of siphonophores are long and thin, consisting mostly of a clear gelatinous material. Some deep water species have dark orange or red digestive systems that can be seen inside their transparent tissues. Siphonophores are exceedingly fragile and break into many pieces under even the slightest forces. Many siphonophores are bioluminescent, glowing green or blue when disturbed. All siphonophores are predators, and use their many tentacles to capture crustaceans and small fish.”
Probably the best know Siphonophore is the Portuguese Man o War (Physalia physalis). Its venomous tentacles can deliver a powerful sting.
Heritage Library general site: http://www.biodiversitylibrary.org/bibliography/6513
Heritage Library siphonophore site: http://www.biodiversitylibrary.org/item/18411#page/5/mode/1up
Dr Casey Dunn’s site: http://siphonophores.org/
Video of Siphonophores: http://www.brown.edu/Faculty/Dunn_Lab/index.php?subject=Home