286 NATURAL SCIENCE. Oct., 



eager he was to elucidate the whole natural history of these animals, 

 although the projected monograph never reached completion. 

 Through these researches a new light was shed on the origin of the 

 marine fauna of Scandinavia, and on the whole time intervening 

 between the Glacial period and our own, during which northern 

 nature was still under arctic conditions. Thus the discoveries of 

 Loven initiated arctic research in time as well as in space. In other 

 words, they have given rise to a long series of papers by the 

 naturalists of all lands on the relations of modern seas to those of 

 the Glacial period : but in this research it must be admitted that the 

 naturalists of Sweden still take the lead. 



But this early work of Loven has been obscured, not by the 

 mists of time, but by the surpassing brilliance of his later work, in 

 which he deserted the Mollusca for the Echinoderma. The two 

 great memoirs, "Etudes sur les Echinoides " (1875) and "On 

 Pourtalesia, a genus of Echinoidea " (1883) showed at their best both 

 his breadth of view and his unwearied patience. In the whole range 

 of Echinoid literature there is nothing that can compare with these 

 two masterly works. The monograph on Pourtalesia gives the result 

 of a searching investigation into the varying structure of the test in 

 the species of this genus. The "Etudes" is an analysis of the 

 composition of the test in a series of representative genera of sea- 

 urchins. Before this time there had been no means of determining 

 the orientation of the test in the Regular Echinoidea ; Loven dis- 

 covered a number of almost microscopic characters in the ambulacral 

 plates around the mouth, and these enabled him to determine the 

 anterior segment of the animal. The position of the madreporite 

 (the sieve-like plate by which the water- vessels communicate with the 

 exterior) in the apical system of plates, the distribution of the bands 

 of slender spines known as fascicles, and the slight deviations from 

 bilateral symmetry in the arrangement of the plates, were all made 

 by Loven's patient researches to yield most valuable aid in the 

 classification of the sea-urchins. His work, however, did more than 

 this. His theory as to the nature of the two zones of plates around the 

 anus of the Regular Echinoidea, and the homologies that he maintained 

 between those plates and certain plates in the other groups of Echino- 

 derma, notably the calycal system of the Crinoidea, may or may not 

 meet with final acceptance. But his views proved a most beneficial 

 stimulus to biological thought, and not least to the labours of our own 

 countrymen, while their services to echinoderm morphology have been 

 incalculable. Here, also, he was the first to draw attention to the 

 minute structures to which he gave the name " sphaeridia " and 

 attributed a sensory function. In his later remarkable work " On 

 the Species of Echinoidea described by Linnaeus" (1887) Loven 

 continued his studies on the test of the sea-urchins, especially with 

 reference to that minuter system of ornament which he named 

 " epistroma," and which he believed to be a modification of the 



