988 General Notes, { November, 
the oil-drop could have been derived was the periblast. That 
layer being hypoblastic, so far as its morphological relations are 
concerned, it follows that the pigment cells which are developed 
around the oil-drop in Scomber, Scomberomorus, Chetodipterus, 
etc., arise from the hypoblast.—/ohn A. Ryder. 
Lire History or TuatassEma—This very useful memoir 
deals with a type, the phyletic history of which is very obscure. 
The author concludes that Thalassema is an Annelid in which 
The larva finally finds its permanent home in some cavity in @ 
sand-dollar shell. Here, by means of its preoral lobe, which has 
now become long, flexible and muscular, and by the aid of secre- 
tions from dermal glands, it arranges for itself rough chambers 10 
the sand with which the shell is filled. In this chamber it re- 
mains a prisoner. Here it grows to maturity, completely pet 
_ from external attack. Its only means of communication with i 
_ exterior is through the small oral opening of the sand-dollar she al 
_ and through this it must obtain all its food and cast its sexua 
| products when mature 
_ The speculations of the author as to the origin of irregular seg- 
1H. W. Conn, Studies from the Biolog. Lab. Johns Hopkins University, 1, No. 
