HABITS, ETC., OF OEREBRATULUS LACTEUS. 191 



not put much faith in Salensky's interpretation (45). He 

 distinctly states (p. 253) that the so-called "nerve-cells'^ iu 

 the entoderm " are obviously nothing but glaud-cells, which 

 are partially filled with a deeply staining secretion and have 

 no sensory function whatever." 



In all four of these species, without exception, the fibres 

 connecting the apical plate with the oral ectoderm are mus- 

 cular in origin. Also the elements which Salensky describes 

 as nerve-cells and nerve-fibres are found to stain easily with 

 common muscle stains, while they do not differentiate at all 

 with methylene blue or any other distinctive nerve stain. 

 This should make us somewhat cautious in accepting the 

 apical plate of the pilidium as an exact homologue of that in 

 the trochophore larva of Annelids. 



Bibliography. 



An excellent bibliography will be found in Biirger's 

 monograph (13), which contains a brief abstract of every 

 paper mentioned. Only those papers are mentioned here to 

 which actual reference is made in the text. 



1. Agassiz, a.—" The Embryology of Auloljtus cornutus," 'Boston 



Jouni, Nat. Hist.,' vol. vii, 1863. 



2. Andrews, E. A.— "Activities of the Polar Bodies of Cerebratulus," 



' Archiv f. Eiitwick.,' Bd. vi. Heft 2, 1898. 



3. Andrews, E. A.— "Eilose Activities in Metazoan Eggs," ' Zoo). 



Bulletin,' vol. ii, No. 1, 1898. 



4. Andrews, G. F. — "Tiie Living Substance as such, and as Organism," 



' Journ. Morph.,' vol. xii, 1897. 



5. Andrews, G. F. — "Some Spinning Activities of Proloplastn in Starfish 



and Echinus Eggs," ibid. 



6. Beattie. — "On the Reproduction of Nemertes Borlassii (Linens 



longissimus)," ' Proc. Zool. Soc,' London, Part xxvi, 1858. 



7. Barrois, Jules. — "Memoire sur rembryologie des Nemertes," 'Ann. 



Sc. Nat.' (6), tome 6, 1877. 



