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ventral ganglion -cord of A dm et us. A similar feature is 

 that the epidermis of the branchial region of Vertebrates 

 gives rise to the epibranchial ganglia, that is to say, in 

 Vertebrates, as in Arachnids, primitive sense-organs take 

 part in the building up of the ganglia. 



The Sarasins (41) have also pointed out the resemb- 

 lance of small sense-organs of Helix Waltoni to the 

 "Hugelorgane" of Ichthophis. Here the sense-organs 

 also seem to take part in the building up of the ganglia. 

 A peculiar coincidence is to be found when we compare 

 the brains of Helix Waltoni with that of Admetus. The 

 Sarasins mention that the most anterior portion of the 

 brain of Helix Waltoni consists of very small, darkly 

 stained, and closely packed nuclei, containing no Punkt- 

 substanz, and no ganglion-cells; this portion of the brain 

 of Helix Waltoni they call the accessory brain. The 

 process of the development of the accessory brain of 

 Helix Waltoni resembles the same process in Admetus 

 very closely and conspicuously. According to the Sarasins 

 the accessory brain of Helix Waltoni takes its origin 

 out of the so called cerebral tubes ; by analogy with 

 Scorpions, it is perhaps possible to prove the same for 

 Admetus, though I can only find it by comparing the 

 papers of Brauer (7) and Laurie (29) . Laurie says that 

 the median eyes of Scorpions arise out of an invagination, 

 which takes place just iu front of the Anlage of the brain; 

 he describes the cells forming it as resembling brain- 

 cells, but having smaller, darker-stained and more den- 

 sely packed nuclei; in another paper (31) he states that 

 the brain of Phrynus resembles that of Scorpions in as 

 much as in both cases we find a division of the brain in 

 a part containing smaller, darker, and more densely 

 packed nuclei, and a part with lighter, larger, and Jess 

 dense nuclei, According to Brauer the median eyes arise 

 on a small projection, which lies beyond the invagination 

 mentione-d by Laurie, this invagination becoming deep, and 

 giving rise to an accessory part of the brain. Brauer however, 

 omits to mention whether he found the nuclei composing 

 this part to differ from those forming other parts of the brain. 



