REPORT ON PHORONIS BUSKII. 3 



his figures (pi. xliv. figs. 12 and 13) represent the embryos inverted, unless they very 

 much differ from anything hitherto described. Mr. Busk gave him the benefit of his 

 great experience in considering the affinities of the animal. 



Dr. Anton Schneider^ a few years later published a historical account of Actinotrocha 

 hrancMata, and also some careful original observations with figures on this and another 

 species [Actinotrocha 2^<^Mida), both from Heligoland, where the larval form was first 

 discovered by J. Midler. He mentions the test or tube in which the "worm" (pro- 

 duced by the transformation of the Actinotrocha) lives, and gives a general account of 

 its development and anatomy under the heads of the larval sac, circulatory system, 

 alimentary canal, tentacles, and lastly its metamorphosis into a Sipunculid, 



Kowalewsky, again, in his Inaugural Dissertation in 1867 ^ first clearly pointed out 

 the relationship between the foregoing larval form (Actinotrocha) and Phoronis. 

 Unfortunately the original paper, which is in Russian, has not been seen, but Leuckart's 

 student, Oulianin, has given a digest of it in his (Leuckart's) Bericht for 1867.^ 

 Kowalewsky found that the larval form (Actinotrocha) abounded in March, whereas 

 Phoronis — from September to April — was without eggs. In the early larval condition 

 the alimentary canal and body-wall consist of a single cellular coat, but in the body- 

 cavity is another cellular layer and a muscular coat with fatty bodies. The umbrella- 

 shaped prseoral lobe next appears at the anterior end, and overhangs the mouth ; while 

 rudiments of the arms occur in the shape of three and then five warts. The embryo soon 

 bursts the egg-capsule and swims freely in the water, an anus meanwhile appearing, and 

 the body increasing in length. E. Claparede shortly afterwards mentions that Actino- 

 trocha is the young of Phoronis, and that he had met with the latter in the Clyde.* 



An able paper on the development oi Phoronis, by Elias Metschnikoff," was issued 

 in 1871. He describes the growth from an early larval stage to the assumption of the 

 adult outline — in specimens procured from Odessa, Trieste, Naples, Messina, and Spezia. 

 These he carefully compares with Ivowalewsky's descriptions and accurate figures, and 

 amongst other things he notes the presence of a nerve-cord in connection with the 

 so-called ventral furrow. 



A paper by E. B. Wilson appeared in 1881 * on the metamorphosis of an Actino- 

 trocha which was found in Chesapeake Bay. The author was enabled to corroborate 

 the observations of Krohn, Schneider, and Metschnikoff, and to carry on the develop- 

 ment to a later stage, until, indeed, the adult form was assumed. He describes the 

 blood-corpuscles as developed in solid masses adhering to the stomach-wall near the 

 base of the tentacles, probably in the cavity of a sinus, and asserts that they never float 

 freely in the perivisceral space. The masses break up during the metamorj^hosis, and 

 are carried into the vessels, an opinion which will be alluded to under its proper head. 



1 Reichert und Dii nois-Reymoml's Archie, p. 47, Taf. i. u. ii., 1862. ^ gt. Petersburg, 1867, 41 pp. 2 pis. 



s Archil- f. Naturgesch., Jahrg. xxxiii. Hd. ii. pp. 236-L>38, 1867. * Anncl. Chotop. Naples, p. 409, note, 1868. 



* Zeilsclir. f. wiss. Zoo}., Bd. xxi. p. 214, Taf. xix. and xx. 



''' Quart. Journ. Micr. Sci., pp. 202-218, pis. xiv. xv., 1881. 



