RinZOCEPHALA— LIFE-HISTORV 



97 



Eoscoff, and S.' neglecta on Inachus mauritanicus at Naples. Tlie 

 antenna, by which the Cypris is fixed, penetrates the base of tlie 

 hair ; the appendages are tlirown away, and a small mass of 

 undifferentiated cells is passed down the antenna into the body- 

 cavity of the crab. Arrived in the body-cavity it appears that 

 this small mass of cells is carried about in the blood-stream 

 until it reaches the spaces round the intestine in the thorax. 

 Here it becomes applied to the intestine, usually at its upper 



A B 



Fig. 68. — Development of SaccuUna neglecta. A, Nauplius stage, x about 70 ; B, Cyjiris 

 stage, X about 70. Ai, A^, Lst and 2nd antennae of Nauplius ; Ab, abdomen ; Ant, 

 antenna of Cypris ; E, undifferentiated cells ; F. frontal horn ; (J, glands of Cypris ; 

 11, tendon of Cypris ; M, mandible ; T, tentacles. 



part, immediately beneath the stomach of the crab (Fig. 69), 

 and from this point it proceeds to throw out roots in all 

 directions, and as it grows to extend its main bulk, called the 

 central tumour {c.t), towards the lower part of the intestine. 

 As the posterior border of the central tumour grows down 

 towards the hind gut, the future organs of the adult Sacrulina 

 become differentiated in its substance ; the mantle-cavity being 

 excavated and surrounding the rudiment of the visceral mass, 

 while as the central tumour grows downwards it leaves behind 

 it an ever extending system of roots. When the central tumour 

 in process of differentiation has reached the unjiaired diverticulum 

 VOL. IV H 



