Heymons (1895-1896) has proved by embryological study that in all cases they really belong to this eleventh segment, which in the course of development becomes fused with the tenth.
Heymons (1895) on the Orthoptera, and munication with the outside.
Heymons believes that the " dorsal of A.
According to Heymons, the yolk-cells must be Metameric Segmentation.
The first of these, according to the nomenclature of the mid-gut from the stomodaeum and proctodaeum may be of Heymons (see fig.
Heymons considers that it represents the sternites of the three trophal segments, and that the gula is merely a secondary development.
Eleven of these may perhaps " be considered as true segments, but the twelfth or terminal one is different, and is called by Heymons a telson; in it is placed the anal orifice, and the mass subsequently becomes the upper and lower laminae anales.
The cerci, when present, appear in the mature insect to be attached to the tenth segment, but according to Heymons they are really appendages of the eleventh segment, their connexion with the tenth being secondary and the result of considerable changes that take place in the terminal segments.
In Orthoptera, Heymons has demonstrated the existence of eleven pairs, the terminal pair becoming, however, soon united with the tenth.
Each coelomic pouch - as traced by Heymons in his study on the development of the cockroach (Phyllo- dromia) - divides into three parts, of which the most dorsal contains the primitive germ-cells, the median disappears, and the ventral loses its boundaries as it becomes filled up with the growing fat body (fig.
It is obvious that the hatching of the young as a larva necessitates h After Heymons, Zeit.
Heymons, Die Embryonalentwicklung von Dermapteren and Orthopteren (Jena, 1895) (also Zeits.
Heymons may be especially mentioned.
Heymons (Nova Acta Acad.