TRANSACTIONS OF SECTION D. G75 



quotes his examples ; we have Salpa, and Aurelia, and the Fern, and as many- 

 more as time allows. How can he expect to interest anybody in a featureless 

 narrative, which gives no fact with its natural circumstances, but mashes the 

 whole into pemmican ? What student goes away with the thought that it would be 

 good and pleasant to add to the heap of known facts ? The heap seems needlessly 

 big already. And yet every item in that dull mass was once deeply interesting, 

 moving all naturalists and many who were not naturalists to wonder and delight. 

 The Alternation of Generations worked upon men's minds in its day like Swam- 

 merdam's discovery of the butterfly within the caterpillar, or Trembley's discovery 

 of the budding Hydra, which when cut in two made two new animals, or Bonnet's 

 discovery that an Aphis could bring forth living young without having ever met 

 another individual of its ov/n species. All these wonders of nature have now 

 been condensed into glue. But we can at any time rouse in the minds of our 

 students some little of the old interest, if we will only tell the tale as it was told 

 for the first time. 



Adalbert Chamisso, who was in his time court-page, soldier, painter, traveller, 

 poet, novelist, and botanist, was the son of a French nobleman. When he was 

 nine years old, he and all the rest of the family were driven out of France by the 

 French Revolution. Chamisso was educated anyhow, and tried many occupations 

 before he settled down to Botany and light literature. In 1815 he embarked with 

 Eschscholtz on the Russian voyage round the world commanded by Kotzebue. 

 The two naturalists (for Chamisso is careful to associate Eschscholtz with himself, 

 and even to give him priority) discovered a highly curious fact concerning the 

 Salpse, gelatinous Tunicates which swim at the surface of the sea, sometimes in 

 countless numbers. There are two forms in the same species, which diifer in 

 anatomical structure, but especially in this, that one is solitary, the other compo- 

 site, consisting of many animals united into a chain which may be yards long. 

 Chamisso and Eschscholtz ascertained that the solitary form produces the chain- 

 form by internal budding, while the chain-form is made up of hermaphrodite animals 

 which reproduce by fertilised eggs.* There is thus, to use Chamisso's own words, 

 * an alternation of generations. ... It is as if a caterpillar brought forth a 

 butterfly, and then the butterfly a caterpillar.' Here the phrase bring forth is 

 applied to two very difi'erent processes, viz. sexual reproduction and budding. 

 Chamisso's phrase, ' alternation of generations,' is not exact. Huxley would sub- 

 stitute alternation of generation with geimnation, and if for shortness we use the 

 old term, it must be with this new meaning. Subsequent investigation, besides 

 adding many anatomical details, has confirmed one interesting particular in 

 Chamisso's account, viz. that the embryo of Salpa is nourished by a vascular 

 placenta.- The same voyage yielded also the discovery of Appendicularia, a 

 ■)ermanent Tunicate tadpole, and the first tadpole found in any Tunicate. 



Some ten years after the publication of Chamisso's alternation of generations 



:n Salpa, a second example was found in a common jelly-fish (Aurelia). Not 



a few Hydrozoa had by this time been named, and shortly characterised. 



Some were polyps, resembling the Hydra of our ponds, but usually united into 



permanent colonies ; others were medusfe, bell-shaped animals which swim free in 



lie upper waters of the sea. It was already suspected that both polyps and 



iiedusaa had a common structural plan, and more than one naturalist had come 



ery near to knowing that medusae may be the sexual individuals of polyp- 



•olonies. 



This was the state of matters when an undergratuate in Theology of the 



'University of Christiania, named Michael Sars, discovered and described two new 



'ilyps, to which he gave the names, now familiar to every zoologist, of Scyphis- 



ima and Strobila. In the following year (1830) Sars settled at Kinn, near 



' Brooks maintains that the solitary Salpa, which is female, produces a chain of 

 nales by budding, and lays an egg in each. These eggs are fertilised while the 

 •hain is still immature, and develop into females (solitary Salpaj). The truth of 

 liis account must be determined by specialists. 



- Cuvier had previously noted the fact. 



s X 2 



