Endoskeleton three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal
Rudolf Leuckart of Parasitology). Leuckart is credited with splitting George Cuvier's "Radiata" into two phyla: Coelenterata and Echinodermata. As a scientist, his provided excellent descriptions of morphologic details giving credence to the idea that zoological evolution can be learned through its anatomical changes. Between 1877 and 1892, he developed a series of zoological wall charts that have been used worldwide as teaching aids. In the field of entomology, he conducted investigations into the micropyle and fertilization of insect eggs, the reproduction and development involving members of Pupipara, parthenogenesis among insects, and studies on the anatomy and life history of the honeybee. A