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Updated: May 8, 2025
Leuckart proposed to subdivide the Radiates into two groups: the Coelenterata, including Polyps and Acalephs or Jelly-Fishes, and Echinoderms, including Star-Fishes, Sea-Urchins, and Holothurians.
This implies no difference in the plan, but merely a difference in the execution of the plan. Both are equally radiate in their structure; and when Leuckart separated them as distinct primary types, he mistook a difference in the material expression of the plan for a difference in the plan itself. So some naturalists have distinguished Worms from the other Articulates as a separate division.
"After spending in this way two years in Zurich, I was attracted to Heidelberg by the great reputation of its celebrated teachers, Tiedemann, Leuckart, Bronn, and others.
Tiedemann's lectures were very learned, and Agassiz always spoke of his old teacher in comparative anatomy and physiology with affectionate respect and admiration. He was not, however, an inspiring teacher, and though an excellent friend to the students, they had no such intimate personal relations with him as with Leuckart and Bischoff.
Moreover, nearly twenty years ago Zaddach, a German naturalist, contended that the worms are closely allied in their mode of development to the insects and crustaceans. This confirms the view of Leuckart and Ganin, who both seem to have overlooked Zaddach's remarks. Moreover, the rings of the harder bodied worms, as Zaddach says, contain chitine, as in the insects.
The nuptial flight places her permanently in possession, till death, of the spermatozoa torn from her unfortunate lover. These spermatozoa, whose number Dr. Leuckart estimates at twenty-five millions, are preserved alive in a special gland known as the spermatheca, that is situate under the ovaries, at the entrance to the common oviduct.
The following summer I attended the lectures of Leuckart on zoology, and those of Bronn on fossils. When at Zurich, the longing to travel some day as a naturalist had taken possession of me, and at Heidelberg this desire only increased.
He is a genuine and excellent botanist, and no mere collector like the majority. Neither is he purely an observer like Dr. Bischoff, but a man who thinks. . .Dr. Leuckart is in raptures about the eggs of the "Hebammen Krote," and will raise them. . .Schweiz takes your place in our erudite evening meetings.
They write me from Heidelberg that they intend the place of M. Leuckart in zoology for my young friend. The choice is proposed by M. Tiedemann, and certainly nothing could be more honorable to M. Agassiz. Nevertheless, I hope that he will refuse it.
But it is not my object to give all the classifications of different authors here, and I will therefore pass over many noted ones, as those of Burmeister, Milne, Edwards, Siebold and Stannius, Owen, Leuckart, Vogt, Van Beneden, and others, and proceed to give some account of one investigator who did as much for the progress of Zoölogy as Cuvier, though he is comparatively little known among us.
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