THE MALAYAN SPECIES OF ONYCHOPHOHA. 83 



somite of the oral papillae. Even at this early stage the somite in 

 question has been divided into two parts, one of which is situated in 

 the rudiment; of the oral papilla; the other, with its cavity almost 

 obliterated, lies in a dorso-lateral position. 

 Fig. 11 «?.— This figure represents the twenty-eighth section behind the 

 one shown in Fig. 11 c. It shows a somite being constricted through 

 the development of the rudiment of the muscle on its latero-ventral 

 aspect. 



Figs. 12 a — 12/ (x 120). — These figures represent a selected number of 

 sections, from a transverse series, of an embryo of the same age as the one 

 shown in Fig. 4. The rudiments of all the appendages, twenty- five in 

 number, are present. The antennae consist of several rings more than they 

 do in the embryo shown in Fig. 3, sections of which are represented in Figs. 

 Ua—Ud. 



Fig. 12 «. — This figure represents a section across the antennae, near their 

 base. The brain lobes are cut just in front of their union in the 

 middle line. The most noticeable feature is the divided condition of 

 the first somite (som.^). The two portions of the somite extend the 

 whole length of the antennae. 

 Fig. 12 0. — This figure represents a section across the base of the antennae 

 and through the brain lobes. It cuts the anterior wall of the for- 

 wardly directed loop of the stomodaeum, and shows the two subdivisions 

 of the first somite. 

 Fig. 12 c. — This figure represents a section across the stomodaial region. 



It shows the cavity of the first somite divided iuto two parts (jow.'). 

 Fig. 12 d. — This figure represents a section across the stomodaeal region. 

 It shows the first somite divided into two parts, a dorsal and a lateral. 

 The lateral portion opens into the exterior by means of a canal, the 

 external opening of which is situated internally to the rudiment of the 

 lip and in front of the rudiment of the jaw, the former being much 

 enlarged in this region. The Figs. 12 a — 12 d show the brain {dr.) as 

 an enormous thickening of the ectoderm. 

 Fig. 12 e. — This figure represents a slightly oblique section across the 

 region of the rudiments which develop in the adult into the rings 

 which surround the mouth. The left half of the figure is anterior to 

 the right. It passes also through the canal whicii puts the first somite 

 in communication with the exterior. The endoderm (e/i.) appears as a 

 ring round the stomodaeum, which is developed by an invagination of 

 the ectoderm and which is surrounded by a mesodermal sheath derived 

 from the inner walls of the first pair of somites. 

 Fig. 12y! — This figure represents a section from tlie region of the rudi- 

 ment of the jaws. The section shows the rudimentary mouth-folds 



