The most important results detailed in this paper are as follows:

1. The primitive germinal cells are peritoneal.

2. The ovoid gland is a solid organ, which develops from aportion of the rudiment which gives rise to the primitive germinal cells.

3. The axial and aboral sinuses are involutions of the cœlom, and have no connection with the ampulla of the stone canal or each other.

4. The genital rachis is an outgrowth from the ovoid gland into the aboral sinus, the formation of sinus and rachis proceeding together.

5. There is no evidence of the existence of Ludwig's hæmal system in Amphiura squamata.

6. Both kinds of cells, germinal and interstitial, which are found in the genital rachis, are formed in the ovoid gland.

7. The germinal cells are formed from peritoneal cells directly; there is no evidence of the transformation of the special cells of the ovoid gland into Urkeimzellen.

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