A Division of Worms

Natural History, Feb, 1999 by Stephen Jay Gould

   observation sur, [l'org.sup.on] des vers. dans les vers anneles et qui ont
   des organs externes, le sang est rouge et circule dans des vaisseaux
   arteriels et veineux, leur organisation les place avant les insectes, les
   vers intestins doivent seuls se trouver apres les insects, ils n'ont qu'un
   fluide blanc, libre, non contenu dans des vaisseaux. Cuvier. extrait d'un
   mem. lu a l'institut le 11 nivose an 10.

   (Observation on the organization of worms. In annelid worms, which have
   external organs, the blood is red and circulates in arterial and venous
   vessels. Their organization places them before the insects. Only the
   internal worms come after the insects. They have only a white fluid, free,
   and not contained in vessels. Cuvier. Extract from a memoir read at the
   Institute on the 11th day of the month of Nivose year 10 of the Republic.)

Clearly Lamarck now recognizes a vital distinction between two groups that had once been lumped together into the general category of worms. He regards one group--the annelids, including earthworms, leeches, and the marine polychaetes--as highly advanced, even more so than insects. (Lamarck usually presented his scale of animal life from the top down, starting with humans and ending with infusorians, rather than following the later convention of working upward. Thus, he states that annelids come before insects because they are more advanced--that is, closer to the mammalian top.) But another group, the internal worms(*) (mostly parasites living within the bodies of other animals), rank far lower on the scale--even after (that is, anatomically simpler than) insects. These two distinct groups, previously conflated, must now be widely separated in the taxonomic ordering of life. Ironically, Lamarck acknowledges his colleague Cuvier (who would later turn against him and virtually destroy his reputation) as the source for a key item of information that changed his mind--Cuvier's report (presented at a meeting during the winter of 1801-1802, soon after the publication of Lamarck's book) that annelids possessed a complicated circulatory system, with red blood running in arteries and veins, whereas internal worms grew no discrete blood vessels and moved only a white fluid through their body cavity.

Obviously Lamarck viewed this new information as especially important, for no other anatomical note receives nearly such prominence in his additions, while only one other observation (a simple new bit of information, without much theoretical meaning) merits a drawing. But why did Lamarck view this division of worms as so important? And how could such an apparently dull and technical decision about naming act as a pivot and initiator for a new view of life?

(At this point, dear reader, limitations of space trump the prospect of immediate gratification. And so, with great reluctance--and with a request that you direct your complaints to the management, as no author in history has ever objected to more space--I must impose the "Perils of Pearl Pureheart" scenario upon you and beg your indulgence until the next thrilling episode, when Lamarck's worm will, in Emerson's words, "mount through all the spires of form" to ramify its author's view of life. Have a good month hanging from yonder mental cliff! I shall return.)