Miscellaneous. 301 



The study of these facts leads, in the first place, to the conclusion 

 that in these animals the spinules and the lamella are developed 

 independently of each other ; and if we take into consideration the 

 relations of these parts to the surrounding tissues, the former 

 belong to the epidermis, and the latter to the deeper part of the 

 integuments — that is to say, to the dermis. Secondly, if we consider 

 these organs in the whole of the class of Fishes, we are led to regard 

 the scales of these Ctenoids as a sort of intermediate type. In the 

 eel, in Rypticus, Grammistes, and certain Blennioi'dei the scale, 

 reduced to the lamella, is subepidermic and destitute of spinules : 

 in the sharks and rays the hard portions of the integuments have 

 quite another origin ; they are epidermic. It will therefore be 

 legitimate in Gobius and analogous fishes to compare the lamella to 

 the deep-seated scale of the eel, and the free spinules to the scutella 

 of the Plagiostomi. — Comptes Rendus, July 19, 1875, p. 137. 



On the Larval Forms of tlw Bryozoa. 

 By M. J. Barrois. 



To the type represented by Aleyonidium may be referred a nume- 

 rous series, the whole of which constitute our first larval form. In 

 all- the representatives of two great divisions of the Bryozoa, the 

 Chilostomata and the Ctenostomata (Alcyonidiina and Vesieulariae), 

 the development presents, as in Aleyonidium, three principal phases : 

 — 1, segmentation to the thirty-two stage ; 2, formation of the gas- 

 trula, and production of the bell-shaped stage ; and, 3, histological 

 differentiation and completion of the organs. 



The first two phases are identical throughout, and the bell-shaped 

 stage is always reproduced with the same regularity. The third 

 stage, on the contrary, may differ according to the genera, and the 

 greater or less importance of the changes produced in it ; we pass 

 through all states of transition, from the most simple forms, as nearly 

 as possible representing the bell-shaped stage in a permanent state, 

 as in Aleyonidium, to the most complex and aberrant types. It is 

 among these last that we must place Cyphonautes and the larvae of 

 the Vesieulariae, which we shall take here as examples of forms thus 

 modified. 



The phenomena which occur in Cyphonautes during the third stage 

 of development, after the bell-shaped stage, may be reduced to two 

 fundamental processes : — 



1. The furrow which will form the disk, instead of being produced 

 in the middle of the dorsal surface, is produced near the summit, 

 from which results a considerable reduction of that organ and a cor- 

 responding extension of the uniting membrane, which thenceforward 

 forms the greater part of the dorsal surface. 



2. The ventral surface tends to become invaginated inwards, and 

 the crown to begin to close above by applying to each other its two 

 opposite margins ; in this way the vestibule and the bilateral form 



Ann. & Mag. N. Hist. Ser. 4. Vol. xvi. 21 



