302 GENERAL SUMMARY TO 



anterior margin and drop just beyond the pallial membrane, hanging in clusters from 

 the setae, presenting the appearance of a white powder, though with a simple lens the 

 individual eggs are plainly seen. They are opaque and spermaceti-like in colour. In 

 the course of a few hours they become clothed with cilia. The sexes are separate." He 

 could not, however, ascertain whether the eggs are fertilised after they have left the parent 

 or before. In some cases the eggs did not appear to be locomotive until two or three days 

 after their discharge, while in other cases they become active on the day of their discharge. 



Fritz Miiller, in 1860 and 1861, contributed some observations on the embryo of 

 Biscina ; x and M'Crady in 1860 offered the first description of the larva of Lingula? 



In 1874 appeared an admirable memoir by Prof. Kowalevsky ' On the Development 

 of the Brachiopoda,' published at Moscow, and of which MM. Oehlert and Deniken 

 have given an excellent summary in French. 3 



Dr. J. F. Van Bemmelen, in his memoirs on the structure of the shells of Brachiopods 

 and Chitons, 4 &c, says that in the species he has investigated {Terebratula vitrea, Tere- 

 bratulina septentrionalis, Waldheimia cranium, and Rhgnchonella psittacea), the sexes 

 are separated, and he supposes the impregnation to take place in the sea-water, into 

 which the eggs and spermatozoids are evacuated through the genital tubes, because he 

 cannot believe spermatozoids to enter the body-cavity of females by the small external 

 openings of these ducts. 



The embryos of the following genera and species have been carefully examined, and it 

 has been abundantly shown that the embryo assumes a series of well-defined stages in its 

 development. Little, however, was known with respect to the embryology of the 

 Brachiopoda previous to the publication of Prof. Lacaze-Duthiers' admirable memoir, 

 to which we have already referred. Thus we have knowledge of the embryology of — 



Terebratulina septentrionalis, by Oscar Schmidt, Morse, Kowalevsky, M'Crady. 



Terebratula vitrea and the variety minor by Kowalevsky, Bemmelen, Oscar Miiller. 



Waldheimia cranium, by Bemmelen. 4 



Argiope (Cestella) neapolitana, by Lacaze-Duthiers, Kowalevsky. 



Thecidium mediterraneum, by Lacaze-Duthiers, Kowalevsky. 



Mhynchonella psittacea, by Bemmelen. 



1 " Beschreibung einer Brachiopoden-Larva " (Reichert und Bois-Raymond, ' Archiv fur Anatomie 

 und Physiologic,' p. 72, 1860, and Wiegmann's ' Archiv,' p. 53, 1861. 



2 " Notice on a Larval Brachiopod," ' Proc. Elliot Soc. of Natural History of Charleston S. C.,' 1860. 

 These authors showed that the larvas of some Brachiopoda swim in a free condition, have a digestive tube, 

 dark or ocular spots, and auditive vesicles. In his admirable memoir on the ' Embryology,' Prof. Morse 

 publishes a translation of Fritz Miiller's paper. 



3 'Observations sur le developpement des Brachiopodes," 'Archives de Zoologie exp. et gen.,' 2nd 

 serie, vol. i, 1883. 



4 'Over den bouw der Schelpen Van Brachiopoden en Chitonen,' 1882; and "Untersuehungen uber dem 

 anatomischen und histologischen Bau der Brachiopoda Testicardinia " in ' Jenaische Zeitschrift fur Natur- 

 wiasenschaft.,' 1883 ; and 'Annals and Mag. of Nat. Hist.,' 5 ser., vol. ii, p. 379, 1883. 



