112 PHYLUM MOLLUSC A 



gland, and opens into the mantle cavity by means of a large, thick- 

 lipped aperture to the left of the rectum. 



Two pairs of prominent accessory glands are present in the 

 female, the large, white, finely striated nidamental glands, which 

 cover up most of the other organs of the visceral mass, and 

 beneath them the much smaller accessory nidamental glands, 

 which are pink-colored in life and lie to the right and left of the 

 rectum ; both pairs of glands open at their forward ends into the 

 mantle cavity. These glands secrete the egg capsules, which pro- 

 tect the eggs after they are laid and while development is going 

 on within them. 



Exercise 7, c. Make a drawing of the female organs. 



The Nervous System. In the position of the principal ganglia 

 the squid resembles the snail, but these ganglia are difficult to 

 observe in a dissection because they are compactly massed to- 

 gether and are protected by a cartilaginous capsule, which forms 

 a sort of skull. The cerebral or supraoesophageal ganglia form a 

 large mass above the oesophagus ; broad commissures join it with 

 the suboesophageal mass, which is composed of the visceral, pedal, 

 and, in front of the latter, the brachial ganglia. Connected with 

 the sides of the cerebral mass are the two optic nerves, which 

 widen out to form the large optic ganglia, and running forward 

 from it are two small nerves which connect it with the suprapha- 

 ryngeal ganglia, a small mass above the hinder end of the pharynx. 

 From these ganglia small nerves pass around the oesophagus to 

 the pair of subpharyngeal ganglia. From the forward surface of 

 the suboesophageal mass, that is, from the brachial ganglia, ten 

 nerves pass off to the arms. These may be seen on the inner 

 surface of the head after the removal of the pharynx. From the 

 hinder surface of the visceral ganglia pleural nerves run to 

 the stellate ganglia in the mantle. Trace these nerves from the 

 stellate ganglia to their source. 



The Pen. Make a longitudinal sHt in the mantle on the back 

 of the animal and remove the pen ; it will be seen to lie quite 

 loosely in its sac. 



Exercise 8. Draw the pen. 



