(With Plates 18 and 19.)
While following the metamorphosis of the larva of Ciona intestinalis last year (1892) in the Zoological Station at Naples, I noticed several peculiarities in the behaviour of the nervous system which apparently could not be reconciled with the account relating to Clavelina which was given by Éd. van Beneden and Charles Julin in their work on ‘Le système nerveux central des Ascidies adultes et ses rapports avec celui des larves urodèles.’ The first assumption to be made was that the conditions might be different in Ciona from what they were in Clavelina, as I had already perceived how much the general development of Clavelina was modified in the direction of a compression of the ontogenetic processes. But on making preparations in toto of larvæ of various ages of Clavelina lepadiformis I could see, as far as the hypophysis is concerned, nothing at all like the...
