SEGMENTATION OF THE HEAD 



11 



labrum ; 

 maxilla 

 palp ; s 



are only connected with the maxillae by membrane : hitherto they 

 have been interpreted as being the palpi and galeae of the maxillae. 

 On anatomical data only, 

 Hansen's conclusions appear 

 to have much in their 

 favour. He does not lay 

 much stress on the value of 

 embryological evidence and 

 only briefly discusses the 

 work of Folsom (1900) on 

 the development of 

 Anurida. In this connec- 

 tion he states that the pair 

 of developing lobes (_p. in 

 Figs. 4 and 5) associated 

 with the first maxillae are 

 the fundaments of the 

 maxillulae. Folsom, he 

 maintains, has misinter- 

 preted them as being maxillary palpi, 

 receive no support from the embryological studies of Philiptschenko 



(1912) and of Silvestri (1932). 

 These observers find no traces 

 whatever of a maxillulary 

 segment either in the form of a 

 neuromere, appendages or coelom 

 sacs. The lobes identified as 

 maxillary palpi by Folsom are 

 shown by Silvestri to develop 

 into those parts as stated by 

 the first-mentioned writer. 

 Cramp ton (1921) made a rather 

 superficial study of the whole 

 question and claimed that the 

 maxillulae of Hansen are homo- 

 logous with the paragnaths of the higher Crustacea which are 

 non-appendicular in character. Hansen, in discussing Crampton's 



Fig. 4. Ventral aspect of the head region 

 of an embryo of Anurida, showing 

 developing appendages. a, antenna ; 

 /, oral fold ; h, hypopharynx ; I, 

 le, leg ; m, mandible ; m\ 

 m", labium ; p, maxillary 

 superlingua. (From Folsom.) 



Hansen's views, however, 



Fig. 5. Head and first thoracic 

 segments of embryo (about 1-20 

 mm. long) of Japyx major. 

 Lettering as in Fig. 4. Adapted 

 from Silvestri. 



