ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 369 



The author discusses the advantages and characteristics of the 

 different kinds of coloration, and concludes by suggesting that the 

 phylogenetic development of the separate varieties is to be explained 

 by supposing that the unicolor examples are the oldest. When the 

 dark contents of the intestine became apparent, " white chromato- 

 phores " must have been developed. Bands would appear in relation 

 to a habitation among marine grasses, and doubly-banded forms would 

 imitate the marking of the ^os^era-leaves. A further change of 

 environment would add to the advantage of the possession of spots in 

 the markings. 



Vermes. 



Annelids of the Canary Islands.* — P. Langerhans has some 

 observations on the anatomy of Syllidete, where he has found in all 

 species of the genera examined a canal in the strong oesophageal teeth ; 

 in SylUs aurantiaca he has been able to make out the poison-gland, 

 which is a paired tube lying dorsal of the oesophagus. He has studied 

 the process of reproduction by fission, and has addressed himself to 

 the question as to whether the same individual once or repeatedly 

 produces, asexually, sexual forms. The result is in favour of the 

 latter, or Krohn's view ; the time between the productions varied 

 from 25 to 49 days, but he never observed the production of more 

 than two sexual forms. Each bud, as it broke away, carried with it 

 a number of the parent-segments ; nearly all tbe segments of the new 

 person contain generative products. There does not seem to be any 

 difference between males and females, but three forms of head are to 

 be distinguished. Of the 57 species noticed 9 at most are new. 



Anatomy and Histology of Terebellides Stroemii t — J. Steen, 

 in describing tbe cephalic region of this annelid, says that it is 

 extremely interesting to observe under the Microscope the working 

 of the delicate tentacles ; they are pushed out in all directions, and 

 may become extended so much as to be longer than the body. They 

 carefully test all the bodies they desire before they seize them. They 

 are provided with a delicate cuticle, below which is an hypodermis, 

 consisting of elongated cylindrical cells. Below these there is a thin 

 transversely striated membrane, comparable to the supporting lamella 

 of hydroid polyps. Below this, again, are the longitudinal muscles, 

 separated by interspaces of various sizes. The spaces thus included 

 are filled by a plexus of connective tissue, and the separate fibres are 

 thickened at various points, and are provided with distinct nuclei. 

 The transverse dissepiments, seen by M'Intosh in the tentacles of 

 Magelona, could not here be detected. After some account of the 

 thoracic and abdominal regions, and a description of the characters 

 which distinguish Terebellides from Terehella, the author passes to 

 his histological observations. 



The dermo-muscular tube consists of the ordinary four layers ; 



* Nova Acta -Acad. Caes. Leop.-Carol., xlii. (1881) pp. 95-124 (2 pi.?.). 

 t Jen. Zeitschr. f. Naturwiss,, ix. (1882) pp. 201-46 (3 pis.). 

 Ser. 2.— Vol. III. 2 B 



