and Anatomy of the Echinodermata. 369 



That we find the ventral longitudinal canals of the Asterida 

 again in the Echinida I have already shown. 



But what we do not find in the Echinida (and Spatangida) 

 are the septa, the longitudinal partitions of the ventral longi- 

 tudinal canals with hollow spaces developed in them, the true 

 blood-lactinse. This may be explained in the following way : 

 In the Asterida, as the more ancient forms, the central ner- 

 vous system remains throughout life in the ectoderm, where 

 it originated, while in the Echinida at a certain time it sepa- 

 rates from the ectoderm and moves into the longitudinal canals. 

 In the Sea-urchins the longitudinal canals {i. e. the canals 

 indicated as perihsemal spaces in the Starfishes) are traversed 

 throughout their whole extent by the five ambulacral or radial 

 nerve-trunks. By this means of course a development of 

 partitions or septa is rendered impossible. If we speak of 

 perih^mal canals in the Starfishes, in the Sea-urchins we 

 must call them perineural canals. 



These perineural canals have no connexion at all with the 

 system of blood-lacunaj. The lacunar ring, whicli in the 

 Starfishes runs round the oesophagus, has in the Echinida 

 come to be situated upon the lantern, and from it start the 

 lacunge to the intestine and the glands. 



In schizocoele-formations of the back the blood-lacunae run, 

 in the same way as in the Asterida, in septiform structures. 

 Moreover the Asterida and Echinida exhibit similar struc- 

 tures in the blood-lacunee running to the sexual organs. 



In Starfishes a schizocoele-space runs to each sexual organ 

 and is continued in lacunge of the connective substance of the 

 wall of the organ. But in each schizocoele-space there runs 

 also in the suspensory band a blood-vessel (according to 

 Ludwig's designation), which is connected with the glandular 

 organ. I regard these canaliculi also as conductive lacunee 

 for the glandular organ. The cells in them will certainly 

 have taken up materials from the sexual organs to be conveyed 

 towards the glandular organ. That excretory materials are 

 found in the lacunae of the wall of the sexual organ may be 

 easily proved by sections. Deposits of granules, sometimes 

 of a brownish, sometimes of a yellow colour, occur every- 

 where. Nay, it has even been said by one naturalist that 

 the sexual organs, at the time when they do not form ova or 

 semen, function as glands ! 



In the Echinida the anatomical character is the same. In 

 them also schizoccele-spaces pass to the organs and enclose, 

 the peculiar lacunge situated in the walls. The foundation of 

 the sexual organs is the same in both groups. Nay, the 

 figures which show the sexual organ in the Echinida still in 



Ann. & Mag. N. Hist. Ser. 5. Vol. xx. 26 



