PROBLEMATIC DUCTLESS GLANDS AND THE BODY CAVITIES. 



The branchial or "blood" gland, and the "white bodies" are both isolated 

 masses of tissue and are probably blood glands. The former is long and somewhat 

 flattened, and forms the center of the core of the gill. It is composed of large 

 oval or cuneate cells, radially arranged around the blood vessels, from which 

 they seem to be separated by a vascular endothelium. Joubin, however, believes 

 that the gland cells form the entire wall of the blood vessels. The gland has no 

 apparent physiological connection with the gill and is not connected with it except 

 through a branch of the anterior aorta which passes thi'ough the gland and 

 anastomoses with the branchial arteries. 



The four white bodies (Plate HI Fig. 22, W. B. & W. B.') are compact and 

 smooth and are wedged in between the optic ganglia and the eyes. One lies above 

 and behind each optic nerve, another below and in front of it. The glands are 

 richly vascular and then- veins open into the optic sinuses which surround the 

 glands. The cells of the glands are small and are composed of a relatively large 

 nucleus and a small cell body. They are very similar to the blood corpuscles and 

 are closely packed without definite order. Mitoses are very common , and there 

 seems little doubt that these glands produce the blood corpuscles. The glands 

 arise from the ectoderm. 



The Body Cavities. 



The vascular system of the squid, is lined throughout by an endothelium 

 which is formed of thin flat cells whose edges are irregular or sinuous. The 

 muscular and connective-tissue coats of the arteries and veins become gradually 

 thinnei- as the vessels become smaller until they disappear leaving a vascular 

 wall formed solely by the endothelium. The vessels thus formed branch and 

 anastomose profusely so that they make a complex net-work in the tissues. These 

 vessels are the capillaries and may be recognized not only by the simplicity of 

 their walls but by the fact that repeated division does not reduce the size of the 

 vessels. The primary body cavity of molluscs consists of the unwalled lacunae 

 and blood-spaces into which the arteries, and from which the veins, open. Such 

 cavities do not exist in the squid unless possibly in the tissues of the hearts. 

 The sinuses ai-e all lined by an endotheUum and no tissues except possibly those 



