Miscellaneous. 1 7o 



eion by means of a traction exerted upon these pigment-sacs. 

 Under the old explanation expansion would be the active and con- 

 traction the passive phase ; and, indeed, a stellate form has been 

 described as the result of the dragging produced upon certain points. 

 M. Harting has never seen this last appearance ; he has only some- 

 times recognized the existence of processes resembliug small diver- 

 ticula. 



According to M. Harting, all the cbromatophores of the embryos 

 of Loligo are situated immediately beneath the epidermis, in the 

 layer which will afterwards become the dermis, and which then 

 presents the ordinary structure of still amorphous connective tissue. 

 Each of them is placed in a small flattened cavity, in which it can 

 effect its movements of contraction and expansion. Without pro- 

 nouncing any decided opinion, M. Harting thinks it probable that 

 there is a very delicate parietal membrane. He was unable to 

 ascertain the existence of a nucleus ; but this negative observation 

 is not of much value, as F. Boll says expressly that the nucleus is 

 very difficult to distinguish in Loligo. 



Although M. Harting did not succeed in recognizing muscular 

 fibres inserted upon the periphery of the cbromatophores, he never- 

 theless ascertained the existence of fibres of another kind, from 

 twelve to twenty of which radiate round each chromatophore. Each 

 of these fibres terminates towards the chromatophore by an inflated 

 part containing an ellipsoidal nucleus. Under a very high power 

 the terminal inflation shows four or five longitudinal striae, ^^■hich 

 may be traced into the slender part of the fibre, and which perhaps 

 indicate that the radial fibres are themselves composed of a certain 

 number of much more delicate fibres. M. Harting has never seen 

 these fibres continued into those of a neighbouring chromatophore ; 

 but in proportion as they depart from the chromatophore they be- 

 come paler and paler, and seem to lose themselves in the midst of 

 the surrounding granular tissue. It is nevertheless possible that 

 they may change their level and be continued into the muscular 

 layer. According to M. Harting, these fibres do not unite to form, 

 as Boll supposed, a wall round the chromatophore ; they are, on the 

 contrary, isolated and independent of each other. M. Harliug's 

 opinion is that the power of expansion and contraction resides in 

 the protoplasmic substance of the chromatophore, and not in the 

 fibres or cells which surround it. He thinks that the fibres are of 

 nervous nature, and that under their influence the cliromatophore, 

 by its own activity, executes the movements of which it is the seat. 

 By examples dei'ived from what is observed in the cells of the walls 

 of the heart in the embryo oi Loligo, in many Infusoria and Grega- 

 rinse, and in the cbromatophores of the chameleon, he shows that 

 analogies are not wanting in favour of this view. — Niederlandisches 

 Archil' fiir Zoologie, vol. ii. 1875; Bibl. Univ., Bull. Sci. December 15, 

 1875, p. 432. 



