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The discovery that Notch, a key regulator of cell fate determination, is functional in the vasculature has greatly improved our understanding of differentiation and specialization of vessels. Notch signaling has been proven to be critical for arterial specification, sprouting angiogenesis, and vessel maturation. In newly forming vascular sprouts, Notch promotes the distinction between the leading "tip" endothelial cell and the growing "stalk" cell, the endothelial cells that eventually form a new capillary. Notch signaling has also been implicated in vessel stability by regulating vascular mural cell function. More recently, macrophages carrying an activated Notch have been implicated in shaping the course of new sprout formation. Tumor vessels abide by similar principles and use Notch signaling in similar ways. An exciting discovery, made by several researchers, shows that blocking Notch function in tumor vasculature provides a means by which to suppress tumor growth. The authors discuss the developmental and physiological role of Notch in the vasculature and apply this knowledge to an overview of how Notch targeting in the tumor environment can affect tumor angiogenesis and growth.

FOURTEEN FIGURESWhile investigating the dermal elements in the fins of some of the North American catfishes it hecame apparent that the morphology of the spines is closely correlated with the the arrangement of certain soft parts into organs. Ohservations upon the de\-elopmcnt of the spines in the common bullhead, Ameiurus nehulosus, and the spines of both young and adults of other species, revealed not only the truth of this conjecture, but also the fact that the spines of these fishes possess a peculiar mode of growth after the dovelopmental period is passed.The catfish spine represents an association of lepidotrichia as do the spines of acarithopterygian fishes, the difference residing in the manner in ~jr'hicl1 these elements are consolidated into the definitive structure. The lepidotrichia which contribute to the formation of the spine first appear as enlargement of the basement membrane as in the case of soft rays described by Harrison ( ' % ) I and Goodrich ( '04)2. Eventually the scleroblasts succeed in surrounding and separating tlie incipient lepidotrichs from the basement membrane. The completeness of this separation appears to vary.'Harrison, R. G. 1893 Uebcr die Entwicklung der riiclit knorpelig vorgebildeten Skelettheile in den Plossen der Teleostier. Arehiv. fur mik. Anat., Bd. 42, S. 248.On t h e dermal fin rays of fishcs, liviiig and extinct.

Renal myxozoanosis was diagnosed histologically in 11 captive, wild caught, adult weedy (common) sea dragons, Phyllopteryx taeniolatus, from three separate public aquaria in the United States. Myxozoan spores were visible in wet mounts of kidney tissue and were associated with renal tubular dilatation and tubular epithelial cell hypertrophy. Light and electron microscopy revealed spore morphology consistent with the genus Sinuolinea. Spores were spheroidal, slightly dorso-ventrally compressed, length (L) 17.1 x width (W) 16.4 x thickness (T) 15.6 microm, with two shell valves joined at a distinct, sinuous sutural ridge, and had two nearly spherical polar capsules, L 5.5 x W 5.0 microm, with five to seven turns of the polar filament. There were no extra-valvular ridges or protrusions. DNA sequencing required the design of three new primers that yielded 1740 bp of 18S ribosomal DNA sequence. The parasite was determined to be novel based on morphological and molecular data, and was given the name Sinuolinea phyllopteryxa after its vertebrate host.

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La morfologia del aparato transmisor del sonido en 10s anfibios caudados y su significaci6n filogenktica.E n 10s anfibios dotados de cola existen dos tipos morfol6gicos de aparato transmisor del sonido. E n el tipo mas generalizado, la columela y el opkrculo son distintos, en lo referente a la fusi6n de una con el otro. E n el otro tip0 10s representantes de la columela y el opBrculo e s t h fusionados entre si, formando de este mod0 una placa fenestrada. Esta particularidad hace posible la divisi6n del conjunto del 6rden en dos legiones: una que incluye a 10s Amblystomidae, Cryptobranchidae, Salamandra, Triton y Diemictylus, y 10s Sirenidae; la otra que comprende a 10s Necturidae, Amphiumidae, Typhlomolgidae, Plethodontidae y Desmognathidae. El aparato definitivo generalizado es Gtil solamente en el medio ambiente terrestre y debe haberse originado en conexi6n con este medio. Las formas que actualmente son acu&ticas han adquirido secundariamente este modo de vida. Otras tienden a1 mod0 de vida acuAtico, mientras que algunas han retenido las costumbres terrestres mas primitivas con la correspondiente estructura y mod0 de desarrollo.

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No. 3The Columella Auris in Amphibia.