2 Reticulated Basement Membranes in the Submaxillary Gland 
is a very incomplete one with very loose protoplasma bridges, easily 
broken and easily united to allow the cells to wander in all directions 
during the earlier stages of development. So it may be that the syn- 
cytium as seen in the tadpole 8 mm. long has existed ever since the 
appearance of the mesenchyme.” The apparent discrepancy between 
these two statements concerning the primitive condition of the mesen- 
chyme may be explained from the fact that Mall’s problem is not to 
solve that question but simply to trace the development of the con- 
nective tissues from the syncytial stage. The other problem is still 
unsettled, but, at the same time, not the least suggestive work is that of 
His which is quoted by Mall. 
Now in tracing the development of the connective tissues Mall con- 
sidered not only their simpler and more elemental relations, but also 
in a general way the manner in which they enter into the formation of 
certain organs, as, for example, the intestines and the framework of 
lymph glands. Reticulum he regards as distinct from white fibrous 
tissue, but concludes that it represents simply an embryonic form of 
that tissue. Together with reticulum, white fibrous tissue, the frame- 
work of the cornea, bone, and cartilage, must all be classed as collage- 
nous. While it may be true that the framework of the lymph glands 
resembles a more embryonic type of white fibrous tissue, nevertheless, 
in other places reticulum shows peculiar, highly specialized adaptations 
to the needs of organs of which it forms the framework, suggesting 
the probability that morphologically, at least, it may represent the 
highest development of any of the fibrillated products of the syn- 
cytium. Such adaptations, for example, are beautifully shown in the 
framework of the submaxillary gland and many other organs. 
It will be the province of a later paper to discuss the development of 
the exoplasmic fibrils in the submaxillary of the pig from the simple 
syncytial stage to the complex relations which they show in the adult, 
indicating at the same time some of the physical factors that may be 
involved in bringing these relations about. The specific point of the 
present communication, however, is to show how the reticulated base- 
ment membranes are formed from the primitive syncytial products. 
Throughout the literature and throughout the history of the develop- 
ment of the basement membrane idea, the question has been raised with 
considerable discussion whether or not these structures were homo- 
geneous or fibrillar. Many investigators have maintained from the 
first that basement membranes in general were homogeneous, others 
showed with apparent conclusiveness by numerous digestive and pre- 
cipitative methods that they were composed of reticulated fibrils. More 
